ls swappers opinions needed

[sbc10guy]

Hi guys i have been looking into an ls1/t56 swap into my 69 c10. I wasnt able to get my donor car last weekend as he just let me know he had a loan on it yet. The kicker is i am able to buy my last truck back right now. My deal is im torn between doing the swap or buying my old truck back. My last truck is my dream truck i was forced to sell. Its a 71 cheyenne shortbed ls1/4l60e. Frame off restoration with my favorite color combo. He wants 21000 and its ready to go. This or build mine i figure il stick 15000 into the swap to do it the way i want it. The truck looks like i just pulled it out of a field which i know is in right now but im sure is not worth what it could be. I just want to make the right decision financially and not have 18000 into a truck worth 5 or 6 when its done. what would you guys do? The blue and white truck is the 71 and the green is a pic of the 69 last weekend at my hunting land