Relatively simple transmission upgrades

I bought a used automatic transmission for my truck while I rebuild my broken transmission. The transmission I got has 190K on it as looks to have been rebuild at 143K (I can just make out ?43-?/?6/12) as I doubt it was rebuilt at 43K. I dropped the valve body to get a look at the bands and they look almost new, not a spec of burning on them and the front band is measuring at aprox. .055" of friction material left (it was tight to get the caliper in there.)

I'm not looking to do a lot of work to the trans as it must go in before it starts staying in the 40s, i'm justing looking to get a year or two out of it or at least until I can rebuild the other one. What is a relatively cheap and easy upgrade to the trans or valve body to increase life/shift quality. I've heard of a manual lever that allows fluid flow in park, is there anything else? I've already got a trans cooler half the size of the A/C condenser that its going to run through.

TransGo shift kit and fluid changes are your friend.

If it hasn't had a shift kit installed it should. Might change the governor pressure sensor and the OD/Lockup solenoids.
If you haven't ....removing the check relief valve is a good idea.
For heavy usage, a transmission temp gauge is almost a requirement.

Okie and DD94 have you very nicely covered. Only thing i would add is nice large cooler and 100degree tstat for the cooling lines. They combined with the temp gauge is a KILLER combo for making sure the thing lasts