Can finally afford to do a few mods...the engine is bone stock 400...no idea on heads or year 72-76 from some donor pontiac in Alaska.
will be a daily driver and family car and very basic horsing around in... [Quote]
The least exspensive route would be a Comp Cams XE series cam. There has been a little contraversy about them in the past concerning wear and failure, but if you follow the break in procedure you shouldnt have any problems.
If it were me , I would run a Comp cams XE 262 in your 5000 LB tuna boat.
Stock compression ratio is 8.0 to 1 if you have the # 7J2,7K3, or 4X heads. If you have a 1973 or later engine it will have lower compression heads and some power making capability will be lost.
First thing to do is to ID the motor you want to run. Get year date code from back by the distributor.Also engine casting number. Then get the numbers from the heads.the number will be on the top of the center 2 exhaust ports.
Seeing that you have a 455 in bare form, that would be your best bet to build.
First, you would be able to keep the 400 you have as a runnig spare, and if you are going to spend money to build an engine, dont take apart a perfectly good running engine, build a non runner, end up with 2 engines.
Also the 455 will make better power for the street with your heavy sled. There is no replacement for displacement.
Quadrajet carbs and stock pontiac intakes work real good for a street build, and would be an attribute to your 455 build.
If it were me, I would build the 455.
Fact is stranger than Fiction