More pictures please! I am about a week away from mine being completed. When I saw your picture for a second I thought it was one my avionics shop sent me. Your 1977 J has a very similar interior to my 1975 F. As for the panel question. I think the better avionics shops have the equipment to cut a new panel for you. When I stopped into my shop yesterday, I saw them cutting a new panel for a plane.
My upgrade is a PFD Pro/MFD 1000, Garmin GTN 650 and a PS Engineering 8000BT. I'm interfacing to a STEC 60-2 and an existing Narco 12D+. I had the STEC upgraded to a ST-670 flight director and Aspen is now providing code for full AP functionality during regression (through a switch the shop built for me).
For those asking about pricing, I had a number of quotes done for the Aspen and they all came in within a $1K of each other. And the prices were no where near the $15k prices you guys are talking about. PM me and I will give you the specifics of my quotes. There is an Aspen rebate through the end of the month for the connected panel with the PFD/MFD. Also keep in mind that quotes will vary quite a bit depending on what you want to interface.
I spent a lot of time digging into the details of the upgrade path, so if you have specific questions on hardware configs, I can provide some guidance. My fire hose activity now is taking in all of the new functionality I never had before.