i found a parts manual for a d3400 genset on ebay, i'm assuming i can use it for my 3j d2 as well???? i'm hopin, its pretty cheap...

Well, u'll be missing a bit of the tractor!

I expect the governor would be different for starters. Without the serial number reference, you won't always get on the right side of any improvements and modifications even to the basic engine.

Look one up on the CAT literature site and call and see what you can get a real nice copy for before you spend much on it.
www.cat.com/cda/layout?m=90800&x=7

There's a couple guys on these boards that have a D3400 generator set, so maybe it will be "trade goods"