What Fred says is correct, on board is not critical, but nice to have if you have the extra bucks. I have the SuperGlo by MPI, about $45. It can be used manually from a switch on the Tx, or controlled through the throttle so that it comes on at a settable point, usually about 1/4-1/3 throttle, and goes off ,too. The on-board glow lets you start up without having to connect an outside battery source, but you pay a weight penalty of the additional battery on-board. The Warhawk can easily afford the weight.
If you just want the remote plug, it allows you to connect the glow starter at a point away from the engine when it's hard or impossible to get to the glow plug, such as the inverted mounted engine on your P-40. Find an easy to get to spot, but one that doesn't detract from the appearance of the plane, to mount it. That's waht I also like about on-board glow, nothing shows.
Look at
www.maxxprod.com for the SuperGlo.