manual conversion isnt a cheaper options. alot of work and labour is involved.
not too sure if theres much difference between the r34 NA and turbo gearboxes, but the only place i found that does shift kits for turbo r34 gearboxes is MV Automatics in Adelaide.
only searching up for turbo gearboxes, i found out with a shift kit, you will benefit alot shifting wise (from what i have researched) shifting is almost immediate with throttle released and 0.5~1second with full throttle. which is a huge different comparing to the standard 2~2.5seconds. also with a shift kit it doesnt flare causing friction that builds up heat. heat kills gearbox.
i received my stage 2 shift kit and 2800/3000rpm stall couple days ago so hopefully it will be going in sometime early next week. if you like, i can let you know what differences i felt with then two items in. cause when i tried finding out about the two not much was mentioned.
with my shift kit it was $350 for the shift kit, $91 for core deposit (you get it back when you send back your standard valve body) + freight. not too sure how much different it will be with a NA gearbox (if theres any difference) also remembering labour cost for removing and refitting the valve body if you're not doing it yourself. its also a good idea to find a 2nd hand gearbox so your car isnt off the road for the time its all getting done (in a week or so roughly)
but if you interested in a shift kit i highly recommended MV Automatics as they are reknown for automatic skyline gearboxes and theres a fair few members on sau using their products. call Mike on (08)83700430