Will a honda shadow 750 motor fit in a shadow 600 frame?

Will a honda shadow 750 motor fit in a shadow 600 frame? - 1

YES! All you need is a Saws-All, some bushings, an arc-welder, a different swing-arm and if all goes well we'll see down the road. (why I ride Triumph, All their engine fit, no matter the Model or Year, LOL!)

Not without "help".

As I've said many times before, you can make almost anything fit almost anything else, if you have the skills, knowledge and experience to make all the neccesary modifications (or, you can afford to pay somene who can).

The real question is, do you?

Actual year of engine, actual year of frame needed to figure out how much cutting/welding might be required. Later models tended to have frames and engine mated, the old motorcycle industrial practice of one frame for a couple different engine sizes, model variations no longer applies usually.

Bolts right up.

The 600 VLX is a completely different softail style frame. That 750 will only go in after much modification. For the same money you could simply fabricate a new frame. Or buy one used.