outboard to inboard conversion

[taqwache]

ok here is a good one. i got a 78 V20 steplift that has been in the family since 1979. it came from the factory with twin 75hp mercs. after 10 years or so of saltwater use, those went bad and my dad repowered with a single 175 mariner. now after another 10 years or so of saltwater use, it has also gone bad along with the transom. since then the boat has been sitting for 5 plus years in his back yard. now me and my dad plan on restoring it. i found this site and noticed that these boats also came with inboard/outboards which is what i want to use. since the whole transom needs to be replaced anyways, how hard would it be to just mod it for and inboard/outboard? i was planing on useing a modified 400hp 6.0L gen3 chevy with a mercrusier alpha one. i know it will be difficult but that does not matter. i am very mechanicly inclined but i dont have to much boat experience. although i can learn very quickly. i can build a motor for almost free but i will have to buy all the other marine parts. what do yall think? what else is different from the two styles of boats (OB and IB/OB) that will be a challange?