Got an older wby 340 with the tupperware stock. It's probably a early 90's vintage...jap built I think by Howa. Anyhow its a fussy shooter and I was checking to see if the barrel was free floated and it's not. It even has little pads molded at the front of the channel to make pressure point at the tip.
There are also support ribs that seem to make contact ahead of the front action screw.
QUESTION: Are there any reasonable improvements that can/should be made on the stock....if not has anyone got a replacement stock idea that isn't a small fortune??

B&C makes a nice upgrade. I have taken the nubs off a tupperware stock and it should be better for you. The stock has a lot of flex but could be easily bedded. This is cheapest.

You might want to try another stock. I have one that you can have for the price of shipping. If not just buy a new B&C or you will go nuts trying to get the old one shooting properly. Not worth the agravation.

Jack up the optics and replace everything that's bespoiled by the W'by name under them?

If it was my Howa, the first thing I'd do is get rid of the foam rubber stock and install one made out of natural materials (IE: wood)

Hold it. Don't do anything till you talk to a 340 owner.