I changed a TBI to carb once
I used a regular fuel pump on the block and pulled the fuse out for the fuel pump ,
The fuel pump on the block will pull fuel through the electric pump with no issues ,
I got rid of all the fuel injection stuff on top of the motor and cut the fuel line going too or coming from the fuel tank and made it go too the fuel pump on the block .
Used a stock G.M. electronic distributor and ran a wire into the fuse box into something that only runs with the key on .
I worked just fine till the van got so rough it had to come off the road .
I am not sure why you are are changing the system but I already had a rebuilt 69 four bolt main motor sitting here .