I'm inheriting my grandfathers 1980 D250 standard cab all stock. My question is what's the biggest size tire I can put on it while having no extra lift? I'm looking at a set of 33" but don't have the truck yet to check proper fitting.
Thanks in advance,

Provided the springs aren't sagging an abnormal amount, you can fit a 265/75/16. This works out to just under 32".

What size are the rims? 16"? 16.5"?

I believe the rims on the truck now are 16.5 I'll have to check when I get the truck

If they are, you will pay more for 16.5 in tyres than if you bought new wheels and tyres in 16in. I went thru this about ten years ago and am sure it is worse now for even finding 16.5in tyres that you would want.

I have my eye on a set of 16" rims, the rims I'm looking at are 8.5 wide though, will that rim work with a 265/75/16 tire and still clear the breaks and fenders without rubbing on a stock D250?

i have never seen a 16in wheel that won't clear the brakes on a 8lug that had a 16.5. I used 16X10s on my Ramcharger that had a 8lug awap and they cleared fine. And they were thick Alcoa alloys and I had 33x12.50 super swampers on them.

Ok thanks everyone for all the help, now if I use an 16x8.5 rim with 265/75/16LT tire on my 1980 dodge D250 what backspace or offset should I use if any?

I believe the wheels I'm (usually) running are a 4.25"ish backspace, and are 16x7. They are factory ford aluminium wheels.

I have a set of stock Dodge Steel wheels in 16/8 on my Chevy 3/4ton pick up. It had 13in HD brakes on the rear, and big rotors on the front and everything clears well. The back tyres are about the same size (metric) as a 35x12.5.