Tyre sizes

[MacQuigley]

I am a way away from needing tyres for my truck, but while I wait for parts I may as well gather information.

The wheels fitted to my C10 ar3 15 x 8.5. Currently they are fitted with a mix or tyres in 2 sizes 215 x 65 x 15 and 225 x 60 x 15.

To my eye both sizes look too small on the rim and Id like to go for something like 235 x 75 x 15 or 245 x 70 x 15 (even 245 x 75 x 15).

Can anyione tell me what the max size of tyre that I can fit on a 8.5" rim and if anyone has fitted these sizes were there any problems when you fitted the wheels to your truck.