I've been running the carb tank in the elky for about a year now. You have to keep alot of gas in it since it is not baffled. As far as the pump goes, the whole sending unit is internally the same, but like the other member said, the ring & seal and piping above the tank is different. I actually use the gn sending unit in mine, but dont recommend it. If you buy a new tank, where are you getting it from???? they dont make em, as far as I know. I bought one, and had to return it since it was not baffled. They looked it up and noticed the same part number for the fuel injected elky tank was the same for the carb. tank!
and they are all made by the same companys. You'll have to find a sending unit and tank from a 86-87 4.3 efi elky, which is very hard to find, and as for the fuel lines, you cant take out the gn lines and shorten them, thats redicilous. You'll need to run a new line, and you can use the 2 existing lines for the return and the vent. My problem now is fuel! I have too much fuel pressure that wont adjust at idle, and drops at wot. something is going on with my wiring to the pump, I guess I should have had somebody do it
good luck.