How many miles are on this engine? And how does it sound any knocks or was it over heated ? If this is the factory engine it is a 4 bolt main 350. You will be using the short block only . The heads are #882 or #624 not good castings for a build up . You will want to go with Vortec heads or S/R world heads . Does it matter if you use center bolt valve covers on your rat rod . I think the GEN 1 4 bolt type look better for a rat rod build ? Let us know more about your engine so we can help you pick out your cam intake carb . The TH400 trans should be a short shaft 400 that will work out for you . Also what rear gear are you running ?