I get the reminiscing bit but realistically you are unlikely to find Yammy limbs of this vintage in this draw weight. Custom limbs would put you back way more than it is worth. The YTSL II was a good riser but is prone to corrosion issues, so it may last forever but equally might break after just a few shots.
Buying secondhand limbs would be an OK option, I just don’t think you’ll find any. Might be worth checking the dealers in the Netherlands where Yamaha were very popular.
My recommendation would be to buy an entry level kit for a couple of hundred quid and see where it takes you.
Stretch