If you are a stickler for details, just skip this advice. I also had problems fitting the spare in the original tub (didn't know that about the repro tubs, though). I replaced the front tub floor hangers with longer sections of threaded rod with double nuts on the bottom as retainers. The extra space up front allows the tire to JUST fit up and into the tub.
The #match crowd goes :ugh when they see it but I only notice it when it's up on the lift. No biggie.