My Two A/C units

90 XJ - r134a, works good.

88 MJ - r12, no worky.

Question: What is involved in converting from r12 to 134a. I know I have to have the system evacuated, flushed AND refilled and but what's involved parts wise.

Nipple adapters
Compressor
Accumulator/Drier
Expansion valve
Hoses.

The above 5, I can handle installing. Trying to save a buck but do it right.

Can I just recharge it now with some Freeze 12 and the correct oil. I'm a cheap mofo!

If the compressor, hoses, evaporator and expansion valve are in good condition they can be reused. The r134a adapters never seem to work well I used these http://www.nostalgicairparts.com/air-conditioning/tube-o-suction-and-discharge-fittings-with-r-134a-port-591.php it's a complete replacement for the older tube-o fittings. Replace all the o-rings with r134a compatible o-rings. Replace the condenser and upgrade to a larger one if you can. Have the system evacuated and flushed. The compressor can be flushed with PAG oil. All the old oil needs to be removed from the system since it's not compatible with the new stuff. After it's all assembled get it evacuated and filled.

I wouldn't use Freeze12 it's not a direct replacement for r12. For how old your system is it's better to switch to r134a and replace some parts. Something is probably broken and leaking anyway.