Colour me pink -- I just noticed the land-based application thing.

That still doesn't change the need to operate the engine within its optimal performance range. It should be propped so that unloaded at speed, its rpm reaches but doesn't exceed the power peak. I haven't seriously played with a prop driven car for years, although I still mess around with snow buggies made from the fuselages of crashed planes (someone else's crashed planes of course).

If acceleration is not a big issue & peak speeds can develop, I think that the prop diameter should be fairly small, so that the pitch could be maximized for high ground speed. Drag is still an issue, so some testing will be necessary, but speeds near 100 mph should be possible. The stock 40 LA can turn a 9-6 at 13,400 RPM (static) -- right on the peak -- but it will unload at speed, so a bit more pitch could be tolerated. It will also spin an 8-8 at about the same RPM -- and that will really get a ground vehicle moving. If the engine can be tweaked (piped, for example) to both increase power & RPM, the 8-8 should also still work well. If an 8-9 can be found, & if the vehicle drag is low, it should also work.

If the vehicle is used in very short bursts, as you surmise, then a much flatter pitch prop will be needed, since the coarse pitch prop will be at or near stall at low speeds & will provide very poor acceleration. In that case the bigger the diameter the better, but since he is limited to ~ 10", typical aircraft props are probably more suitable. A 10-4 would turn at ~13,400 static and would obviously be very good for rapid fire bursts of speed & still not seriously over-rev the engine.