I have a 77 spectra 18' that has a ~400hp 454. The pump I i believe has an A impeller, is all stock appearing including the rock grate. it does have a hydraulic place diverter. I am looking for some more mph from this boat. I plan to go to a b impeller and new wear ring during the off season but would like to try some other things out in the meantime. My question is what would be the next item(s) to try. I have been looking at the ars bolt on shoe and ride plate. Thanks!

More mph is on the efficiency of the hull, and thrust. You need to improve one or the other, and usually both.
Going to a "B' impeller will increase rpms. It may or may not improve mph. What rpm are you seeing now? An impeller swap to a "B" will be a ~300 rpm increase. Will the engine withstand that?
My old sled, a 73 Glencoe 19', did 71.8 mph, gps'd with ~500 hp, @ 5200 rpm.
More info is needed to form a good plan on your boat.
If the bottom has a huge hook, that's the first thing too address.
Then on to pulling the intake to machine for a ride plate and shoe. A loader would be next.
Then add horsepower, as much as you can afford.

Just my $ 0.02

Dan'l

For what it's worth depends how much money you want to spend ? Do you want  dependable turn key or break shit and drive the crap out of it, work on it and break it some more  I did the latter but I'm crazy  person ,so  start out slow , ok your parts buy good parts not junk high dollar race parts are great for race boats not for weekend boats  that you cruise  with the woman and kids the pump parts are just as important  if not more than the motor , get yourself a good oil pan 10 quart milidon sells a great one don't get a big cam ,iron heads hogged work great,   unless you got the money for aluminum call GEORGEat ARS for the pump and listen to the guys here,  keep it reliable ,just my 2 cents

Sounds like you got it covered Ryan , I have a 468 big chev 9.8 compression same 049 heads with big valves and ported ,victor junior Intake and 1000 cfm AED carb flat tapped solid cam ,eagle rods steel crank arp bolts on a 2 bolt main block  motor runs to 6000 I'm running 83mph 12.5 in the 1/4  but it was the pump GEORGE did for me that got me there, stainless impeller B cut,  inducer with a droop and a ride plate and diverter in a 78 sanger , love it pump gas reliable,  went to a stroker 489 last year spent a ton of money solid roller big cam motor broke more parts I live in riot city  Portland oregon it's a short year as well the high spring pressure solid cam and not running  it every weekend  plus my dumb ass not turning the motor over enough to get the spring pressure not sitting broke the roller lifter wheel went threw the motor and broke the block these were comp cam parts fixed it again and  broke again , I've run the crap out of the 468 motor and always put the motor back in after the other one broke ,the guy who built the stroker was a good race engine builder for circle boats just my luck I guess , was just saying my experience in the last 12yrs of jet boating got me back reality, by the way I got a broken stroker motor for sale haha

Bummer the nice motor didnt stay together for you. Have the droop and ride plate always been on your sanger? If you installed them did you do before and after testing? is your intake machined for the plate or is it an add on deal?