what has anyone done to replace the fuel pumps with a modern electric replacement/conversion? 1966 3.8 S dual SUs

 

No, and why would you want to ?
After market electric fuel pumps run all the time and they wear out. (brushes/commutator wear out, like a fuel injected vehicle, it will just stop one day and leave you stranded)
Many of them are junk made in China.

If you rebuild the original SU pumps with modern circuitry, they last forever.
Even the old ones went for decades with no service, like 30+ years.

There was one in my Bentley when I bought it. it had a tendency to push fuel past the float needle valves _ too much pressure.

 

Recommended vendor and instructions?

 

Burlen Fuel Systems will sell you an updated but traditional SU fuel pump. The update does away with the points and switching is electronic the pump part remaining the same.

http://sucarb.co.uk/su-fuel-pumps-sp...tive-9017.html

 

The SU's are tried and tested, you can get repair kits from Burlen too, either overhaul or replace with another SU as Fraser has said.