I have a 1971 Chevelle turbo 350.. when driving ..when I push the gas there is a clunk..sometimes..sounds like a ujoint to me..but I looked and there isnt any play in them..but neither are there any greese fittings..could these be the original joints?should I just replace them..also I noticed the transmission mount seems to have alot of play in it..

I would suspect the trans mount. There should be very little "play" only the rubber stretching a little.

can the transmount be replaced without taking the crossmember out?what would make the clunk noice if the transmount is bad?

Did you take the drivesaft down and 'feel' the u-joints? I've seen them where they feel OK spinning them while bolted up and tight & notchy when you drop them.

So can I replace the trans mount without dropping the crossmember?should I replace the ujoints too?

So can I replace the trans mount without dropping the crossmember?should I replace the ujoints too?
yes you should be able to replace the mount w/out removing the member.
also I would replace the joints while your under there.

I would replace the trans mount first and see if that makes the klunk go away.
Only 3 or 4 bolts.