Check Italeri for 1/72nd Huey kits, know they did a hog never saw a medivac, know they did a slick. In 1/48 both AMT and ESCI(same kit I think) did a medivac Huey. Hasagawa may have done a medivac in 1/72, but I don't remember for sure, know they did a slick,
You could convert the interior of the slick without to much work.
John
helicopters don't fly, they beat the air into submission