19.5 tires running mixed brands and ratings

Some of you older guys can remember when we used larger heavier tires on the rear that were the norm on pickups back in the '60s/'70s era. A 7.50-16 on the front and 10.00 or 12:00 on the rear. No handling issues after the best psi for the job was found.
Some of the old 16.5" truck tires came in huge sizes.

Common problems you will run into can be different tread type such as a mild HT tread vs rough AT tread tires or new tires on the rear can show a bit of tread roll till the tire is broken in.

thanks all!

I had the same go-around with Pep Boys about putting 2 new tires on the front of the Taurus (front wheel drive). They would NOT do it. Said they MUST put them on the rear.

I politely explained to them that the front axle-

-carries most of the weight of the car
-does all of the steering
-does all of the driving
-does most of the braking
...and more importantly, that's where I want them, and I'm the one paying the bill!

There was still no convincing the guy. So I asked for the manager. An arguement ensued with him.

So, I walked out, went to Discount Tire, and they put 2 new tires on the front axle, no hassle or arguements, at a better price too. I never went back to that Pep Boys tire/service dept for anything again, but I did leave them a few gallons of dirty oil of various types, all mixed together, and some used coolant on their doorstep, a few times over the years.

It looks like you are running a 2WD. So, no problem fore to aft with keeping the loaded radius the same. Just keep the same (actual) tire diameter on each side of the axle. Also, remember that the load on the front axle does not change much with the addition of the TC. You seem well over-rated with wheels and tires, so I would put the G rated on the front and the H rated on the rear unless you want a more aggressive tread on the drive axle, then make that choice. It just doesn't matter. On a 2WD, almost every tire installer recommends having the best tires on the rear, for safety reasons. I had this go-round with 2 new tires I bought for my Chrysler 300M and wanted on the front. Costco said they would only mount them on the rear, not the drive axle. They were snow tires. Snow tires don't do much good on the non-drive axle.
The only other consideration is the wheel width. Some 19.5's do better with a narrower wheel; some are built with a wider wheel in mind. It's the way the bead fits to the inside of the rim and why any ".5" tire (16.5, 19.5) tends to walk off the rim at low pressure. Most mfgrs. post a range of recommended wheel widths with their tire stats, whether those wheels are actually available or not.
jefe

right now I'm running 70-75 PSI unloaded at all corners. When loaded I pump them up to 90 PSI at all 4 corners

I don't think you are going to notice much difference, but it has more to do with air pressure than the rating. I'm assuming you probably running about 100-110. You are probably running 15-30 lbs more pressure in the rear than fronts, so the rears will still be stiffer than the fronts.