Going to 18" rims questions

Wanting to upgrade my '68 Barracuda to 18's since good quality 15's are getting rarer by the day.

It has a rebuilt stock front end, small ball joint spindles, SSBC 153 disc conversion, upgraded sway bar, with factory small block T-bars. Rear has a Strange S60 Dana rear with 11" drums, stock spring location, and sway bar.

I don't like the looks of most 17"/18" wheels. However, I did find some that are meant for suv/trucks and hoping I will be able to go with them. They are only offered in 18x8 but two different backspacing/offsets. One is 10mm offset with a 4.89" backspacing and the other is 35mm offset and 5.87" backspacing.

If I'm correct in my thinking, from all I have read on here, I think the 18x8 with 35mm offset and 5.87" backspacing version is what I need. Please correct me if I'm wrong!

Now, the even more confusing part to me is which size tires front and rear should I run. I'm hoping for sizes that are relatively easy to find at most tire places (this will be a daily driver) and hopefully not look like I'm riding on rubber bands. I know I gotta keep the front under 26" in height since I don't want to permanently modify the fenders if I don't have to. I'm thinking a 245/40 for the front. Rear I would like to have a little bigger tire to fill up the wheel well a bit but have no clue.

I know I still have to measure everything to know for sure but if I get the rim choice figured out I'll be able to figure out the most tire I can squeeze in on the rear. Any input pointing me in the right direction would be appreciated.