Other differences:
Early D doesn't have the "eyebrow" over the binocular sight ports in the mantlet. The D has roadwheels with less outer rim bolts than the A. the A and D also will have different tracks. The early D will have a communication port on the left side and pistol ports on both sides of the turret, the early A has only the pistol ports. The late A production discontinued the pistol port. Some late A's have the monoculor sight and consequently have only one hole in the mantlet.
The early D drivers hatch exterior grab handles are located in the center of the hatch, on the early mid and late A they are outboard. The early D has a fifteen ton jack mounted under the exhaust stacks, the early A has a heavier jack transversely mounted under the stacks, the late A has the jack between the stacks. The D and A drive sprockets are also different (center hub). The early D will have smoke candle dischargers, deleted on all other Panthers. Some early D's had dual headlamps. The early D letter box armored cover is different in that it has a bulge. Early D's can also have a long stowage box on the right hull sponson directly behind the pioneer tools. Early D models had raised brackets over the rear air intakes to mount stowage boxes, not seen on the A. As for the exhaust cooling pipe, or triple exhaust, most early A models did not have this. Complicating this further, there were many D's retrofitted in the field with the A model cast cupola. You can spot these if you can make out the bolt pattern on the roadwheels.
I don't know about conversions, but you can do what I'm doing and build a collection of all variants, I've gone with the DML kits has they exhibit the most variety. If you order the Eduard and Aber deluxe PE kits, they provide all the conversions and Aber provides an excellent instruction manual detailing what goes where on the A and the D.
Good Luck with your Panther project!
steve