Speaking to mechanic about rebuilding my 350

[LuckyScott]

If you ever sell your truck, matching numbers may make a difference. It does on all the other cars from the 70's, why not the blazers?
Pull your motor, stick it under a bench or in a corner and drop in something else. You have lots of options and can do whatever you want, but that original motor will still be sitting there and not loosing any value.