I would buy the new TX with the walnut stock as i think what you pay extra is money well spent. Sell your current TX as a going concern if the stock on it fits well, there is always the chance that if you do swap them over you might not be so lucky. I notice your current TX stock has no checking so a new TX factory stock will be quite a contrast and may take some getting used to. Have to ask the question, why are you going over to the very sensible(in my opinion) .177.

Regards

Barrel