I have 3 SIG kits that can use a similar engine. The kits are Kadet Senior, 4Star60 and Hog Bipe. I have several similar "sized" engines that include OS 61 FX, OS 91 FX, Supertigre G90, and Saito 91 (ringed).
My challenge is to come up with a common mount (one for each engine) that can be swapped (with its engine) between the different models while using the same firewall bolt pattern. (Yes, I understand that the 4-stroke will likely require a different throttle linkage but that is another topic.) I took my engines to a LHS to check out some options. The one I found that fits the bill is the Hayes AL60. This is the "long" version which is necessary for the rear-carbed Saito 91. The 2-strokes don't need the luxury and there is a short version that shares the same firewall bolt pattern.
There ya have it (for what it's worth
) ...