It's a big block engine, sort of.  It's not as big as a 460 and it's definitely not a small block.  It's from the Ford seires of "FE" engines.  HP depends on year, carburetion, etc.  Many different cylinder heads.   If you have one in a boat it was probably around 300HP or so.  Probably my favorite series of engines, since that's what I learned first.  332, 352, 360, 390 410, 427, 428 were the sizes available.  Came out in 58 I think and was used into the 70's in pickup trucks. 

Good motor! I would consider it a Big Block, same as a 396 Chebbie.

2 experiences I have with the 390 were both "police interceptor" versions.  1 was in a '66 Fairlane a bud had when I was in HS. VERY strong 14 second car, and a ton of fun. The other, about the same time frame, we put in my pops old '75 1 ton dump truck.....got the motor cheap, he needed it, why not? 

Truck would pull anything, and haul over 2 tons without a hiccup while towing the little backhoe he had at the time. 

Didn't know anything about ferds back then. Still don't, really, save the 460, but nearly 30 years later that engine still impresses me.

Ray

ya its in my '72 challenger..... all i know about it is that i have a holley 4 barrel single pump, 650cfm carb on it with edolbrock log and snails... other then that im pretty sure its a stock motor.. rebuilt 4 years ago.. atleast thats what the guy told me a year ago... i ran it last year and got a top speed of 55... i have a jacuzzi wj pump