From experience here's how I rate ones I know about: !/16th Fujimi Porsche 959 is very good IMHO !/12th Mono/revell Testarossa is okay,but toylike. Could be worked into a nice piece with some Aftermarket. !/16th Revell Camaro/firebird Very toylike GREAT tires though.
Would have to know if Oil or diaphragm. I have a oil-less diaphragm and when it was struggling I removed the head and found some foreign material in it and cleaned out the cylinders and wiped them down with some silicone spray on a cloth. I think some debris from the plastic filter found it's way in. It was fine after this and still working today.
WoW I think I'll take that resin '54 Merc I have and get started on this!
If you like Plastic you could modify the Lindberg '53 Ford . Just chop the top, modify the rear quarters,scratch up a front bumper/grille and few dozen odds and ends. Just about the time you finish they'l announce a new issue.
Don't know what your build is aiming for but there are 4-speed manual trans in the two Corvettes '57 & '63 . Possibly automatics in the '78 Corvette. There is also a trans in the 1/16th Mustang. This just a few of what's available in 1/16th. there are more I'm sure.