Before the pump is suction side so if you have a cracked or perished hose you wont see it leak it will suck air in. there is a short piece on the chassis rail about under the drivers door and at the tank itself. But if you still have fuel going in when you pump the carbie I'd say its over fuelling or more likely your ignition system check your timing, points, plugs leads ext, Was your new engines cam dialled in correctly? Also a vacuum or intake leak could produce a similar fault, does it stall if you pump the brakes at idle?