I have plans of using a normally asperated 270 Offenhauser engine, from American Racing Miniatures, in a Duece roadster. I want to replace the single speed crash box with a transmission that can handle the power. I know I would need to fab an adaper plate to tie the two together as well as a mounting point for a conventional starter. I had planned to use an electric fan mounted to the radiator which is mounted inside a MCG track nose. Any ideas on a tranny and rear end would be appreciated.
Actually, any 60's muscle-car 4spd would have worked back in the day! The 270cid Offenhauser had its roots all the way back 1935, when Fred Offenhauser first produced those engines--in the days before Hilborn fuel injection, that engine was good for about 250-275 hp or thereabouts, being designed for the prolonged high speed running at the Indianapolis Motor Speedway, but with cams designed more for acceleration than high-speed laps (think one-mile dirt speedways, as from the inception of the Offy out to about 1953 or so, Indianapolis was the only paved speedway in the US).
The 270 ran with dual side-draft carburetors exclusively until fuel injection arrived in AAA Contest Board competition about 1952 or so.
In the early 1960's, some racing mechanic working out of Indianapolis, had a '28 '29 Model A roadster pickup street rod running around, with a 270 Offy up front. I've seen only a couple of grainy pics of it, and that was decades ago now--but I believe it used a pretty much conventional belt-driven fan, powered off the front of the crankshaft (Championship Offenhausers had their crankshaft extending through the front of the engine--in order to provide a splined coupling for a hand-crank(by the late 30's or so, a portable electric starter powered by a handcart of 6-volt car batteries (pretty much as Indy cars are started today.
Fred Offenhauser also built 2 or 3 early 270's having on-board starters, for clients wanting one of those hoary 4-bangers for sports cars in the mid-late 1930's as well. In addition, those engines had external water pumps, to keep the coolant flowing though the radiator, and large, rather thick radiators to handle the cooling (any Offy will run much hotter on gasoline than on methanol--methanol fuel not really coming into use until after WW-II on speedway cars.
I've had the same idea as you--in fact I have a couple of those resin engines, one from ARM, te other having been cast by Chris Etzel back almost 20 yrs ago (Chris mastered, and cast his Etzel's Speed Classics kits about 5 miles from where I live).