'51 frod F1 Donor drive train?

Hi,.Im mew to the site and I will have a load of questions since this will be my first build.

I have a F1 that I want to put a newer drive train (Chevy)under.Im on a serious budget,but I do have access to a slew of options since I work at a scrap yard.Loads of you name it,farm,tractor,industrial,cars,trucks.
I want to go with a SB Chevy,auto trans and rear end.Ill be using several other '50s F series frames to get the stance I want,Z'd at both ends,LOW but safely drivable.F1 axle up front with shorter leafs,maybe a 4 link with coils at the rear.Ive been collecting for some time for this build and Im at the point for my mock up.

Really I need suggestions on the tranny short or long?