I have a (mostly) stock a12 and 4 speed in my
coupe. it runs great for a few minutes then
looses power and stalls. it restarts and runs
poorly from then on. I have replaced the electric
fuel pump , distributer,cap,rotor,wires,fuel
filter,coil and the carburator. now I am lost

Will it do this when stationary? If so bang a meter on the HT lead and see if you lose zap when it is cutting out. Sounds fuel related to me though - let it cut out and check fuel
level in filter and float level in carb. If they are suspect then could have a crimped fuel line or problem with pickup in the fuel tank. You have replaced the carb - what with? Brand
new? Rebuilt? Used? Judging by the photos in your garage the car has sat for some time so could be related? We'll be interested in hearing what the fix is!

Check your fuel line for dirt or rust particles. If you have a small restriction in the line, the petrol flow can cause the particles to accumulate at that spot and partially block the
flow. It has happened to someone I know (although not a Datsun). The restriction was where the line goes over the rear axle. The rust would build up near the top of the hump and the car
would die. Soon after the car stopped, the rust would run back down inside the pipe, freeing the blockage and allowing the car to be restarted again, only for the problem to repeat.
Barry