Can a retired public safety radio like a maxtrak be used to make a GMRS repeater legally? These radios were not/are not part 95 type accepted. (Please site FCC or other Legal source)
You've answered your own question. If they're not type accepted under the appropriate section of Part 95 for GMRS, then they're clearly not legal for use as a transmitter in a GMRS repeater. The same holds true for most other radio services. Amateur is the big exception. Part 97 does not require type acceptance for transmitters, but does have some very firm prohibitions on interference, spurious emissions, etc. Instead of requiring the radio to be technically certified for use in the bands, it places the responsibility on the operator.
There's already a huge body of discussion on this topic. The answer hasn't changed. Look back through the threads in this sub-forum. It's the same debate over and over. Is it legal? No. Can it technically be done? Yes. If I use a Part 90 radio, will I get caught? Highly unlikely, but the fines are significant if your luck doesn't hold.
However, a MaxTrac or other non Part 95 radio could be used as the Rx side of home brew repeater without issue.
Plenty of info at repeater-builder.com about building repeaters. It's geared a bit more toward amateur radio, but all the info is fully applicable to GMRS. Probably the biggest plus is that you would not have to worry about pulling the radio down into the ham band.
There's also a growing body of information at mygmrs.com for the reading. The answer is the same over there.