i had a 1991 beretta GTZ and it came with 5 speed Quad 4 motor. was a nice car too until it blew head gaskets. i think some of the olds model also used Quad 4 too.
From what I heard that was a common problem of the quad 4. The usually blew around 100K is what I was told.
I think your best bet will be a salvage yard. Yea the headgaskets in these motors usually go around 100K miles, and when they do you will usually find a crack between the intake and exhaust valve seats. Its not hard to rebuild them, but I did find that the felpro valve stem seals did tend to leak a bit, so I went back with GM ones and they sealed up fine. Not sure if they packaged them wrong, but the GM ones I had to press on with a socket, and the felpro could be put on with your hand.
webracin