Going to 18" rims questions

Sorry, read that backwards at first time I replied. I don't think a 35mm offset with a 5.87" backspace will work.
You likely can't go any more than a 4.5" backspace on the rear and 4 - 4.5" backspace on the front of a stock suspension.
You only have 5.5" from the face of the drum to the leaf spring in the rear.
Ok, I think I see what you're getting at. I know the offset is pretty important on the front as to not screw up the scrub radius if I recall. Would the 10mm offset affect the handling and safety of the car too much?

Here's my setup on a '67:

255/35/18
275/45/18

18 x 9.5 US Mag Bandit U109

View attachment 1715630482

Sadly, I can't get the rims I like in that width. However, the info on the rims you chose definitely shows me that up to a 8mm offset/5.25" bs should fit. BTW, beautiful ride you have!