A J 72 is very hackable to a J65 . The biggest problem is the awful plastic that some of the earlier ones were made of, very difficult to stick, but there have been quite a few done, not least by Martyn.
the white metal K,s kit can be hacked as well.
I bought a J68 from cdc , the printed one and it is good, fits both the Terrier chassis and a SE Finecast J69 chassis which can still be got as a kit of part.