engine Suggestions needed
Any of the 100cc engines would be massive overkill for this plane. You could fly it with as little as a G-62, MacMinarelli 85cc, GT-80Zenoah, or ZDZ80 single or twin on regular mufflers.
Personally, I'd go for the 100cc twins, then throttle back. BME, DA, or even a used Brison 6.4 are all good choices.