I've got the Testor's issue Porsche 911 Turbo and Lamborghini Diablo. They're both nice kits. They're not completely full detail, but do have opening hoods (it's more of an engine plate than an engine).
Actually, the only short shot kit I've got in my stash is the Jo-Han Chrysler Turbine. The exhaust ducts aren't completely formed on one side. I can probably scratch build the missing part, but you still hate to see it on a classic kit like that.
The 1/20 AMX is much nicer than the Gremlin. The AMX is full detail, so it has a full engine, folding front seats, detailed chassis and suspension and lots of options for customization. It even comes with racing wheels and slicks for drag racing.
The 1/20 scale is actually pretty decent. It has working steering, engine detail is good and overall looks well proportioned. I think it shows it's age a little in places. The dash and interior could be better detailed (it's still a tub-style interior, knobs are just barely bumps on the dash), the headlights are part of the front ends chrome, etc. But it's definitely worth building.