I'm sure the experts will come along soon and give you few recipes / suggestions.  I think there in shock right now, its not often that someone comes along with actual realistic expectations for speed.  Usually people want to know why the stock truck motor they put in there boat wont push there 21' daycruiser to 100 mph. 

78 Centurian with 78 Ford F-250 Camper Special 460 motor pulled straight from truck and into the boat. Odometer read 78000 which we figured rolled over once. GPS'd at 58 mph down river in front of Willow Valley Marina running a panther pump, so you dont even need a new Ford to go fast.

svssr95 - thats good to know! is the pump stock? or have you done any mods to it?? seem to be a good pump for you??

propless - i know that i wont be breaking the sound barier. but i do want to be able to keep up and have fun with my buds out at the lake. themain reason behind be building the chevy is because i already have 4 blocks sitting in the garage and have alot of other stuff for chevys already stockd up.

Personally, the big block Chevy is a good choice, especially if you have pieces and parts lying around ready to play...

The Panther Jet will be your weak link IMHO, build a motor that can turn some RPM and the pump should be fine (say up to 5500 RPM).

This basically takes the tall deck out of the equation....In my experience, a 427 makes a great choice for a high RPM requirement and at the same time, cheap to build (relatively speaking)...

The biggest mistake I see made is the overshooting on the heads and camshaft. I really like oval port heads and high rise manifolds with a somewhat small camshaft. It gets convoluted, but the torque requirement is what make a jet boat motor special. A motor that requires 6500 RPM to make peak power will never get there unless your torque "comes in late"...

There are dozens of "recipes", but if a pump gas non racing toy is what your after, here is what I would build;

427 cu in through 468 cu in big block. Shorter stroke=higher RPM range but less overall torque.

10.0-1.5:1 compression ratio on an open chamber based head (for availability reasons) and forged pistons.

Good blue printed high volume oil pump and over sized "jet" pan.

A marine specific camshaft, preferably a hydraulic roller with a long duration without crazy lift numbers (keeps things tough).
Comp Cams actually makes a few off the shelf sticks that I have had some success with and they are somewhat affordable.

A good mechanical secondary carburetor and exhaust are an absolute must, it would be a shame to build a hard running engine and put a restrictive exhaust and carb system on it..

Next up is ignition, I prefer keeping it simple, but it's easy to go overboard here.....MSD "ready to run", MSD 6 series and Pertronix are all I have ever played with and never looked back, these can be bought used with little effort.

All this being said, I have no issues using old but good used parts, if you have an unlimited budget (I don't) then go to a reputable engine builder that is familiar with marine builds and tell him what you are looking for.

There will be a million opinions out there, but do what feels right and you will be fine.... Just don't over think it...

As for the Ford...I'd rather see you build a MOPAR...   Hi proppy...

GT

Cool! We like pic's     

   I have an 18 ft galaxy with a panther and it has a 396 i put together. It turns 5600 and goes 72mph. The panther i had to rebuild so i tightened it up with some locktite wear resistant putty while I was at it. The whole set up really isnt anything special but it will keep up with most of the boats at the lake. It just has good oiling and good valvetrain. It has a gm steel crank 3/8 rods with good bolts and trw 9 to 1 pistons in the bottom. It has oval ports with 2.19 1.88  stainless valves and a little port work i did myself. I put on a tunnel ram with two 600 double pumps. the valve train is a .600 lift 240 at 050 duration solid roller with a rev kit and good roller rockers and valve springs. I put a 10 qt milodon and a new melling select high perfomance oil pump. The thing will just sit at 5600 like a sewing machine.
  With a 454 i might upgrade the rods to something witha 7/16 bolt like a scat or eagle just bacause the bigger stroke but thats me. I would not run as much cam in a jet boat as I would a similar engine in a car and I dont think you need giant heads either because unless your making huge horsepower the pump is not gonna go over 6000 rpms.
 

What's a rev kit?    Do they make 'em for Olds ?   

Sorry I had too.  I couldn't help myself.

Early August we completed the first phase of the restoration on our '79 19' Spectra jet.  The motor was built for an older intercooled PFM twin turbo setup converted to port EFI, low compression, modest heads, mild flat tappet hydraulic cam.  As vacation was nearing we decided to use the boat in a normally aspirated configuration and shake the whole package down.  An Edelbrock Performer manifold and Holley 850 were added breathing through a standard USCG flame arrestor.

The motor was taken to a local shop that had an engine dyno for initial fire-up and an hours break-in.  At that point the oil was changed, timing was bumped to 34 degrees, and a couple of pulls made.  The peak horsepower was 442 at 4700RPM, max torque was below 4000, falling already at that point, but over 500lbs.  Basically this was a motor you could throw in a work truck and be happy with it.  All this was on 87 octane pump gas.

On taking it to Havasu for vacation we GPS'd at exactly 70 with driver, passenger, and both fuel tanks full.  The tach (once working) indicates 4750 RPM at full throttle.

The magic is in the pump, making use of the torque with a stainless AA impellor without having to buzz the motor.  The boat jumps on plane in a couple of lengths and accelerates hard to full speed.

Just another way of getting down the lake.

Cheers, Mark