Why? I have no idea. My *guess* is that after nearly 35 years, the owner, Chris Hoverman decided it was time to simply be a landlord rather than running a hobby business. He (or his company) owns a bunch of commercial properties in the Manchester area, including the three buildings where MU originally was located.
Have you tried NE Performance Mustang? I've looked at their website, just don't know if it's worth the trip from Southern CT.