At only 1200 H.P. the small block would be very reliable and you sure don't need the twin turbos to get it,a single will make that power easy.our last 406 SB2.2 single turbo made 1777 H.P. at only 20 lbs boost and 2230 H.P. @ 36lbs. in a boat you have a perfect water to air intercooler situation as well. the other thing to think about is fuel,if you want to run pump gas then you probably want to go with a big block at low boost.in either case I would look at using an aluminum block Bill