I have tuned some 350s. One for a friend and 2 of mine. The Tuning does not really get you accuracy that area is accurizing. Tuning deals with making the gun more pleasent to shoot. It can increase accuracy but ususally when the tuning is correcting an existing problem like a leaking seal, broken or weak spring, broken rear guide, and such. The accruizing department is doing things like glass bedding the action, adding weight, shimming or checking stock screws Add screw cups if you can. JB paste the barrel with a brush/dewey rod. Hand Lap the crown with JB/brass screw. These are the basics.
I would strongly recommend tuning with the kit if you can get it. The Artic spring is sweet and I got it matched to all steel front/rear guides. The rear is fitted 0.0005" under the ID of the spring that is what takes twang out of the shot cycle as the spring does not have room to vibrate as much as well as keeping the spring from canting. For the seal please do replace the original diana wiht the apex one. The 350 uses the same seal listed for the 34 series. If you are up to it I would also use his old school buttons on the rear of the piston.
Good shooting.
Spring orig top kit artic bottom.
Holes in forearm will elongate without screw cups over time.
use a spring compressor on the 350 as it has plenty of preload on the spring.
some good stuff.
