There are needle roller kits and needle roller kits of course, but the ones I bought on Ebay were rubbish. Problem with needle rollers compared with bushes is that due to their physical size and their hardness they are quite fragile, and being steel, are extremely susceptable to rust.
I replaced all the needle rollers in a 1990's Suzuki RM250 motocross bike's swingarm and linkages (6 from memory) and the replacement cost was enormous, around the 400 dollar mark just for the parts. The bike had been quite well maintained, but the biggest problem was his infatuation with a pressure washer, there wasn't a hint of grease in any of the linkages, those pressure washers are bearing killers, for sure. I did them all again in bronze and it cost the owner (a neighbour) $20.00 for the bronze and $30.00 for a bottle of JD)
If needle rollers are good quality, a good fit and are well maintained (greased regularly) and not used in wet/cold conditions too often, or subjected to pressure washers, they'll do a reasonably good job, but won't last as long as good bronze bushes with 2 or 3 times the contact area of needle bearings, and generally tighter tolerances, much better load bearing ability and some "self lubricating" qualities etc.
Z1 enterprises are great, I bought a Pingel fuel tap for my Suzy GS1000S there and the service was great. If anyone buys a Dyna ignition from anyone else they've got rocks in their heads. I don't know how good their needle roller bearing kits are, but I'm a lazy bastard, and try to avoid "high maintenance" parts if there's a viable alternative. In this case, there is and it's about half the price. Cheers, Terry.