R12 to 134A w/o replacing parts? Are there going to be problems?

[Mcaanda]

I'm looking at purchasing a 86 GT from a guy that said that the AC was disconnected while the clutch was replaced, and they never re installed the R12 that was lost. I asked that it be taken care of before I purchased it, and he said that it’s not a problem, that he would take care of it for me.

My question is this:
What harm is there to the system when you put 134A in the system when it’s supposed to be R12?

He had the 134A installed today into the system, and I know that the compressor as well as the accumulator / heat exchangers have not been changed to accommodate the new mix in the system. I talked w/ a guy today, and said that they do this all the time, yet there are problems that can, and do arise w/ the improper changing of the gas in the system. He didn’t get into details as he was very busy and asked that I was to call back in 30, so that he can go over the specifics for me, but now they are closed.
< I didn’t get to the phone fast enough, the kid was going berserk and I had to deal w/ that there >

What should I do….I have not purchased the car as of yet, and I'm not looking to get into a high repair bill because of this.
Are there any real problems that can occur because of this:
And to top it off, I NEED AC being that I'm here in the central valley. : ugh, it’s going to get hot soon…. :( :

[wolf]

it dosn't hurt any thing, I've had a couple of cars that where swapped to 134a

[grndlvl]

make sure they replace the filter-dryer and orfice tube and flush the system, and any o-rings in the system should be changed,

[OneQuickV6]

Working at a Parts Store, I see people al the time convert to 134a without changing the drier and other parts...You will need however the newer ports (port adapters really) so that the 134a can be put into the system. The r12 and 134a ports are different, the conversion kit (which included the adaptors, 134a, leak sealer, oil, and valve and hose) runs less than $40.