79 Trans Am 403 Olds

[Kidd-7]

I'm working on my parents Trans Am, helping them out and keeping my inheritance in good shape. LOL.
Anyone have any knowledge of the 403 Olds?
I need to change the water pump, there is an option for a high flow pump and not sure how to tell which one is on there. I've done a bunch of googling and search some TA forums, but didn't find answers.
Thanks.

[HO455]

I have owned several 403 powered T/A's but I never had cooling or water pump issues with them so I can't speak directly to your question. However they are not that different than a Pontiac engine and the impeller design and installed clearance makes a big difference in flow rates.
The stamped steel impeller are not very efficient and I always try to avoid them. 1st photo
A cast iron or machined impeller is a better choice in my opinion. 2nd photo.
I don't know about Oldsmobile cross over of impellers but on Pontiacs the mid 1960's impellers are cast iron with more vanes and they can be retrofitted into the 1970's water pumps.
The clearance between the edge of the vanes and the pump body will also affect flow. Too far from the body and you get poor output. I've seen rebuilt pumps with 1/8" plus of clearance. See the 1st link for a better explanation.
2nd link to a high flow Oldsmobile pump.
Good luck with your inheritance.
https://butlerperformance.com/n-1339...ter-pumps.html

https://flowkoolerwaterpumps.com/pro...-ac-water-pump