cam and carb question

Yes, a mechanical cam has a ball end on the adjusters, the pushrods have a cup up top and are shorter. IF you use these mechanical rockers from the 273, you'll need the stock 273 pushrods to go with them and a mechanical cam as well.

Are the adjusters free and easy to turn?

A mechanical cam and the 273 rocker gear & pushrods are the cheapest way to go. And the rockers adjusters must be free to move and adjust.

IF you go with a Hyd. cam, the new pushrods will be needed. And then theres a choice;

Cup end pushrods for a Hyd. cam and mech. rockers, like the 340 T/A engines. There not the same length as the pushrods you have now.

or

Hyd. rockers. Which can be purchased new from MoPar @ approx. $80, and new pushrods. For use with the Hyd, cam.