after about 2 hrs of online searching found this website. they have instructions too... thought i'd pass this along.

for GM pn# 3905525 ('67-'69 metering valve) only $9.00
https://www.musclecarresearch.com/gm...ing-seal-kit-1

for GM pn# 1233464 ('70 Bendix metering valve) $12.00
https://www.musclecarresearch.com/gm...ing-seal-kit-2

now can anyone tell me where i can get a rebuild kit for my stock distribution block?

 

this site also provides instructions & rebuild kits for GM distribution blocks. owner was very intuitive & helpful.

https://www.musclecarresearch.com/gm-pd-valve-kit-4

 

Great find. Thanks for posting this.