Coys vs. Boss 338-(67 Impala Fastback)

[boynton6spd]

I would love to be able to afford a really high end set of rims and tires, unfornutaly, Forgelines, and Rushforths are totally out od my league right now so I'm looking at Coys and Boss 338 in Chrome.
They are priced similarly but I'm leaning to the Boss as they have a HUGE dealer network and available locally.
I'm wanting 20x10 rear and 20x8.5 front.
Any recommendations on tire SIZE?
Thanks, this site is the "bomb" and someday my 67 Impala Fastback will be done!!