car is an 86z currently running 305 tpi
what size is the stock return line

5/16". Main feed line is slightly larger- 3/8".

thanx for the info now is that evap/tank vent line 3/16 (same as brake line)or ?

ok officially here the sizes for any one replacing stock fuel lines from the tank rubber hoses forward, if its tpi you will probably have

Main fuel supply (largest line) 3/8in
Return line (second largest) 5/16
Tank vent- evap line 3/16
Rear brake line 3/16

these are the lines you should see under the car if you need to replace some

the brake line will be attached to a flexing typ of line at the front if u need to determine which is which.