molallastang.....molalla,oregon..just got handed a fully restored 1966 mustang coupe (parents gave to me) and it has a very tired 289 (only thing they didnt touch) need to try and get 375 to 400 horsepower out of it...is it possible without breakin' the bank? gunna enjoy this site
Depends on your bank and what you have to start with. Generally speaking, 400 hp will cost $3000-$4000 to do right. You can cut that way down if you have superior swap meet skills, get lucky on ebay, have a great short block to start with, etc.
My suggestion would be to buy a good clean late model 5.0 and put a carb manifold on it with a decent cam. You might get that done for $1500 or so.