If your car is 302 now I would start with that since converting it to the 351 later takes 2 sleeves to the cross over pipe added later. For 2500 you can turbo and tune the car and then spend money on getting that power to hook. What real life amount are you to spend on it? As it stands a 302 with a single can make enough power to grenade a t-5 (tremic/t56) and other driveline parts, then you need suspention upgrades and you are also talking a cage if you want to run much at trails just keep that in the budget. This is the way I will be going once I get my other bills paid.