79 1st gen - time for new shoes.

how big can I go without making any suspension mods.

Want 235 or 245 on rear and 215 or 225 front.
Can I shove in some 18's? Or should I take a modest 16 or 17.

 

I would get the Kosei K1 in a 16,7 and 16,8. I think this is offered. The rims are inexpensive and 16's are the only practical way to achieve the width you desire on the FA. Check em out on tirerack.com. Don't mind their fitment suggestion, just check out the rim. Must be in silver for these widths. They have blanks and will drill them for me.
Let me know if you are interested, discount for forum members.

See ya,
Rishie
Automotive R&D

 

Oh yeah, the best part is that they are in the "damn, that's a light wheel," category and then they'll say, "damn, you only paid what?" hehe.

Rish