Hi Gary,
What tank are you building?
Tamiya makes a German tank engine maintenance crew set, kit #35180.
The set includes 2 mechanics, 1 engine for either their King Tiger, Tiger I, Sturmtiger, Panther or Jagdpanther kits, a ladder, fuel drum and a variety of tools and mechanics gear.
Once assembled, the engine just fits into the engine bay of whichever kit you're building.
Tamiya also make a mechanic and engine set for their Kubelwagens, kit # 35220.
Italeri's Panther, Tiger I and Sturmtiger kits have an engine included but they're not as detailed as the Tamiya kits.
Cheers
jjumbo