wheel fitment help

[slolowtaco]

Hey all, new to the forum. I've got a 69 SWB that I'm in the process of replacing suspension and brakes. It's getting 2.5" drop spindles and 2" drop springs out front and 5" drop springs out back. Added sway bars and shock relocation brackets both front/rear. Also is being 5 lug converted as well. I'm looking to see what is the widest rear tire/wheel combo I can run before having to do tubs. I'd like to run a 295/40 on a 20x10 or so in the back and 20x8 out front. Whats the biggest rear tire setups you are running before having to tub? I'm not against it if that's what I need to do, but at that point i'll just end up running a 12 wide wheel. Thanks!