St-300 Transmission upgrades

[68specialpost]

Hello Everyone! I own a 1968 buick special deluxe 350 4 barrel 10.5/1 comp lunati cam and ta-stage one intake. (stock 350 2barrel 9./1 comp) It is paired to the stock 2 speed st-300 trans.
My Question is: Are they any upgrades or shift kits available for these transmissions?
I found the 1966 blue printing for buicks article and there is some upgrades in there for the transmission. I know from 64-67 they used the switch pitch st-300 transmissions, I was wondering would these upgrades work on the 68-72 st-300 transmissions? Are they the same transmission? Other than not having the switch pitch converter? Or am I completely out to lunch?
Please lend me some knowledge!
If there’s nothing I can do to beef this old girl up then I can just go to a th-350 or a 200 metric I have built up at home.

[Dr. Frankenbuick]

Yes, the 68 ST300 is the same as the earlier ST300, but it does not have the variable pitch converter like the earlier ST300. Internal passages are blocked and changes were made to accommodate the fixed pitch converter. This is similar to how a ST400 with variable pitch can be converted to use a fixed pitch converter. The Turbo 350 will fit right in place of the ST300. It will give you an extra low gear and better gear spacing. I don't think the metric is going to stand up to your 350 very well. My V6 regal ate then regularly. I eventually went to a Turbo 350 in that. I think there are better transmissions to be had. The Turbo 350 will outperform a well prepped ST300 even in variable pitch mode. In other words, you could spend more to have a transmission that performs less.

[68specialpost]

I had a Feeling that more work would be needed to up grade the st-300. I Wiil go with the 350 I have in stock. Thanks for the help!!