One of the reasons people haven't been quick to recommend a frame is it's mostly a personal preference thing, so long as it's of acceptable quality and has enough room to fit the engine w/a shiftkit - it's mostly a matter of taste *shrug* There's little that can't be adapted so long as there's room.
A few tips though, the shift kit relies on two pipe clamps (exhaust style) for it's rear mount and another for the tensioning method, I would heartily recommend this simple modification to help diffuse the crimping force applied by the clamp, it's just a cut up pipe that had the same inner diameter as my seat post tube's outer diameter, the pipe halves were ground slightly to match then welded to the clamps;
(click to view any lil pic)
I also made beveled aluminum shims to go between the clamp's flat backing and the steel plate that is the now the main motor mount in order to level my carburetor as much as possible - my seat post having not quite enough of an angle (I also modded the intake manifold to level the carb), the spacing of the jackshaft and the seat post is somewhat limited but there was enough to do this with my build (bottommost shim not beveled as it's just the tensioning clamp);
The only other thing is many cruiser style frames have a little too much
room, there's a plethora of solutions ofc but bear in mind that both the front and rear mounts need to be able to be adjusted to take up the slack of the secondary drive chain so a welded, permanent mount won't work for this application - here's what I did anyway (just a chunk of angle steel and 'nother bit of pipe welded together);
The lil brass doohickey was just to hide the 1/2 round hole... a slave to fashion I be heh