would these work on an 81 elco with 16 inch irocs ..or would i need spacers as well.

Goodyear Gator-back P245/50 VR16

I'm running 245-50-ZR16's on my '78. They fit fine with no rubbing, even in hard corners 8) No air shocks for extra space either, KYB's.

would i have to run the back wheels on the front and front on the back..or can i just run them the standard way..i have iroc 16s

I'm not 100% sure on the offset fittment of the iroc 16's on the rear. You my need a spacer, or better yet, find two more fronts so thier the same all around.