These are your Grandads' trucks? And you're going to whack them up? Mistake of a lifetime.
They might be clapped out junk lying behind the barn but they are family junk that deserves respect. You can purchase something to 'have at' and make mistakes on - reread rfs56trk - learn and when you have enough skill then pick one of those trucks to build.
Imagine the pride of driving a cool '47 in 2047 and it being your Grandads' truck, you only get that oppertunity once in your life.