55.2-59 When to buy engine?

[Bigt94550]

Hi everyone.
I have a subjective question and looking for general advice. I have a 57 chevy 3100 frame off in progress. Chassis is done. I just finished the cab rust repairs and put 3 coats of epoxy primer on it. Bed sides and fenders are in epoxy as well. Doors need rust repairs on inner panels. Hood and front fenders are straight but need paint prep and get in epoxy. Then all body could go together. My wife asked if I am ready to buy the engine and trans. I really don't know. What would be a typical path of reassembly to driving from the point I am at? I also need to sort out the fuel tank relocation.
Sometimes I feel I am close, then start looking at the to do list and think it will never get finished.
Thanks
Troy