It has been determined that my '08 H3 Alpha adventure is in need of a new frame (rusted out). There are not many alpha frames on the market. I see there are far more i5 frames on the market, can I just use one of those? I think I'd need an engine mount conversion kit, but not sure if there would be any other differences. Any advice would be greatly appreciated.

 

From what I can see in the pics that's IMHO not that bad. Cut out bad weld in new metal. Paint and run.
otherwise I would personally just purchase a different h3 and sell this one.

 

 

The body is in great shape and there are about 60k miles on the vehicle, so I am committed to it. Need to find out how compatible other h3 frames are, thanks.

 

Go get yourself a another frame. CANYON/COLORADO frames are compatible with some work.

 

My guess is that the I5 frame is more similar to the Alpha that the Colorado frame is, but that's just a guess. Seems like the only differences would be around the engine only?

 

once you have the v8 and i5 chassis side by side you might be able to modify the i5 with the alpha chassis parts then measure cut and weld into place if those parts are still good and fabricate whats not.
other option is remove the chassis you have and repair it.
jeeps suffer the same chassis damage and they sell chassis repair plates.