4WD and different tires question

I have a 94 K1500 Z71. The other day a blew a rear tire out, sidewall got slit by road hazzard. I had four match Dunlop Rover RV's that were replaced 20k miles ago. Dunlop stop making the RV's so I replaced the two rear tires with Dunlop AT's, same size and profile as the RV's. My question comes down how important is having the same brand and model of tire on all four corners. Truck seems fine in 2wd, however, it has a noticably differnet hum when driving in 4wd with snow on the ground. I would hate to do damage to the drive train. Yet, why go a spend $350 for two more front tires to match the ones in the rear without really having to worry about it.

nah, you aren't gonna hurt anything on a vehicle that old. some of the newer vehicles are very sensitive because of the newer more sensitive wheel speed sensors, but since your truck doesn't have abs, you'll be fine. you shouldn't use 4wd on dry pavement anyways, and if you are on snow or in mud slippage will occur naturally, relieving any street on your drivetrain.

I have a Honda Civic with Potenza RE92 195 60 R 15 tires. Would there be a problem if I used a FIrestone Firehawk 195 60 R15 in one of the four positions?

Thanks.