Replacement neck, '70's Yamaha super bass 600

[Okcmco]

hello. I'm brand new and a fairly new bass player. I have started getting more calls to play bass than guitar which is my main instrument. I also confess to a fondness for vintage Matsumoku and Yamaki instruments. Currently I play a "marquis" by Harmony. Yes it is Harmony' off brand. Haha. It is Japanese, and 70's and a quarter pounder makes it growl. My second bass needs to be set up for 1/2 step down so I bought another. This Yamaha bass is weird, funky and sounds like a million bucks. I payed 285 on the auction site a year ago. Due to the wacky weather in OKLA the neck has moved a lot. I cannot add any more tension to the rod and my luthier says that most of his usual fixes will not work on this bass. Was thinking of selling it but then I am sticking someone else with the problem
So. Replacement neck. I hate to loose the funky 70's Japan weirdness of this headstock but. I was surprised at the price of decent necks. All parts would be 225, nearly the cost of the bass. I see some other necks on the auction site for around 100. I was thing I could get a MIM Jazz bass neck but those are 200. And I considered a used neck but cannot find one for this bass. Plus I might have the same problem. I was hoping to find one from whoever makes the necks for the Indonesian and Korean basses. Then again China is making some good stuff now.
Advice? Eep in mind I am really a lead player so if I used way too many words or talked too quickly or my words are off tempo, please bear that in mind...
OH!? And does it matter if I get a J bass neck or P?

 

[T_Bone_TL]

How has it moved? Bent forward, too much relief, high action?

Keeping in mind that I'm a wooddorker and an enginerd, but would not call myself a luthier, before giving up on the neck you have I'd try some modern materials and engineering on it.

Remove it, loosen the truss rod, press it flat. Perhaps heat it and press it flat - depends how much bend it has when not under tension, and what you want to try.

Route a small flat or very shallow groove on/in the back of the neck. With the neck clamped/pressed flat, glue in carbon fiber TOW with epoxy (not "carbon rods") and let it throughly cure (for most epoxy, applying heat or at least keeping it nice and warm will help with that, too.) Use a slow-curing epoxy, not the 5-minute junk.

Depending on your aesthetic taste, top with a strip of wood, or don't. Clean up the back of the neck, wax/oil or otherwise finish to taste.

Reassemble and see how it does. This is basically adding a major-league tension member in the best position to be effective resisting forward curl due to string tension, while you have flattened the neck under clamps - it could save it, and the associated funky headstock, etc., and some cash as well.

 

[Okcmco]

The neck has too much forward bow. No able to add more tension. I like your idea but I would have to buy a router. I am not a woodworker. We'll see.

 

[Okcmco]

I'm sorry. But what is a TOW? Would I find a carbon fiber TOW at the hardware store?

 

[T_Bone_TL]

Perhaps your luthier could do that part, if not willing to try the whole thing. Or perhaps you could ask around to find someone else with a router who could help you out.

TOW is raw carbon fiber filament, and I'd be surprised if your hardware store stocked it. Hobby shops catering to model airplane builders might be more likely, or you can get it online from composite materials suppliers or on (sleaz)ebay. See this thread (post 3) for greater detail:
Less expensive carbon fiber reinforcement