mine is the original in my 68 chevelle and the clutch locked up.my mechanic advised me to try to rebuild this compressor rather than put a new one in.why not just use a new one(replacement)that is ready to go?any thoughts?it's obvious i know very little about a/c.

When I built a 70 driver ( with a lot of detail ) I bought a rebuilt and then spent some time detailing it , Correct color, Decal. I has been fine. Thats my two cents.
Bob

cost I would guess.

I would recommend a NEW compressor. However, they are about $360.
If you can't swing a new unit, look for a quality reman A6. The lower priced remans sold at the chain parts stores often have issues with noise and shaft seal leaks.
http://www.ackits.com/ doesn't list parts for your 68 on their site, but they should be able to provide the correct A6 compressor for your car. Their reman A6 comps are good quality, I've used a few of them. They run about $150.

Good Luck

Just to clarify when you say "the clutch locked up" do you mean the pulley isn't turning ( the belt will slip and smoke ) with the engine running. If that is the case it means the bearing seized in the pulley. That bearing can be replaced without removing and disconnecting the compressor or the pulley does turn but the clutch plate ( plate at the very front of the compressor ) doesn't turn when the a/c is on. In that case the compressor is seized.

it appears that when the clutch engaged the compressor didn't turn so the clutch just turned untill the surface was burned to smithereens. that's what i could tell.---thanks for the replies.

so your compressor seized up. If your compressor siezed up you will want to have your system flushed. That means taking each individual part out of the car and flushing it seperately, the evaporator may be able to stay in, but do not flush the POA valve. Just blow it out. Depending upon what kind of condensor you have you may have to replace it. If it is a cross flow it will definatly need to be replaced if you have contamination especially if you had aluminum floating in your system. You will then have to replace your filter/drier/receiver (all the same part). put it all back together, leak check it pull a vacuum and your on your way.

Since you have a problem and will have the system apart I suggest an upgrade that will help cooling.

Find a late model cross flow condenser that will fit in your car and adapt it. Measure the hole in the radiator support and find one that will cover the complete hole. You will have to make brackets to adapt it but you will like the result. Buy it new.

Do everything Rod said, do it thoroughly, do it right or do it again and replace more parts.
Do replace the dryer.