I had a set of HotGrips on my old bike and loved them. On cold rainy days the palms of my gloves would give off steam. A couple of weeks ago I tired to put the Show Chrome heated grips on my VN750 and am very disappointed with them.
First let me say that it's easier to buy longer grips than the grips that the bike currently has. So what if they are 1/4" too long, the VN750 doesn't have bar end weights to get in the way. You probably don't want to cut the heated grips down because you could sever the internal wiring and make the heated grip useless.
As for changing the VN750 grips, the left grip is pretty straight forward, however the throttle side has a few nasty surprises in store for you. It's not smooth. It has half a dozen or so plastic ridges that run lengthwise and several flanges on both ends. To try to get the Show Chrome heated grips on, I spent lots of time with a Dremel tool, a file, a utility knife, a drill press and eventually a lathe (just for pressing the grip onto the throttle sleeve permanently). In the end it was such a mess that I'm tossing out the right side heated grip and throttle sleeve altogether (I may EBay the left one away) and I put the stock grips back on. Finding a new VN750 throttle sleeve was a pain, there doesn't seem to be a part number for it so I found something close from MotionPro but it's a 1/2" shorter. It works and I'm so pissed at Show Chrome right now that I don't care that it's 1/2" shorter because at least I can ride now!
I actually like the stock grips, their look and their feel, call me crazy. So I'm going to keep them and try under grip heaters for the first time, something like http://www.denniskirk.com/jsp/produc...fCatId=&mmyId=
You might also want to check out this site: http://www.easternbeaver.com/Main/Pr...ted_grips.html
They have some cool products there like relays and wiring harnesses that might make life easier for you.