Can a NV4500 that is currently mated to a 350 match up to a 6.2?

yep, just need a flywheel

Just the plain 6.2 flywheel or is there a HD aftermarket flywheel out there? If there is, where can I get it?

You will need a flywheel, clutch, and bellhousing. The bellhousing for a 350 gasser will not work with 6.2. The first conversion I did was with a 92 nvg 4500 and mated it up behind my 6.2 TD in my 83 3/4 ton 4x4. I bought a new bellhousing and clutch fork and a clutch master cyl., slave cyl. assembly. My 83 had an original mechanical clutch, but I installed the master cyl. in about the same location as the 86 and up trucks use. I am still using the same master cyl. with my cummins conversion and a dodge bellhousing and slave. Hope this helps.;)

You will need a flywheel, clutch, and bellhousing. The bellhousing for a 350 gasser will not work with 6.2. The first conversion I did was with a 92 nvg 4500 and mated it up behind my 6.2 TD in my 83 3/4 ton 4x4. I bought a new bellhousing and clutch fork and a clutch master cyl., slave cyl. assembly. My 83 had an original mechanical clutch, but I installed the master cyl. in about the same location as the 86 and up trucks use. I am still using the same master cyl. with my cummins conversion and a dodge bellhousing and slave. Hope this helps.;)
I thought the bolt pattern was the same as the chevy SBC/BBC pattern? http://www.dieselplace.com/forum/images/smilies/confused.gif

The bolt pattern is the same. The problem is the diesel starter nose is bigger and usually won't fit into the gassers bell housing.
There are some old cast iron bell housings thith the open bottom from the early 70's the diesel starter can work with though.

Thanks very much guys. Any other tips would be helpful.