So you want to hop up your I-6 huh? Here's a listing of parts that I know of that will help your meek 240/300 with performance.
Modifications using Factory Ford Parts
Parts from the Junkyard Performance Company
The cheapest thing to do for those of you who have a 300
and want to up your compression ratio would be a early 240 head, having
it ported and polished wouldn't hurt either.
I don't know how common the heads with the smaller combustion chambers are, but they do exist.
A cheap way to get yourself less restrictive exhaust flow on a carbed truck is to get a dual exit exhaust manifold off of a Fuel Injected truck(1987-1996) With some porting, they can flow just as well as headers, but they won't have that "sound" headers do.
I experimented with using the intake manifold off of a F/I truck, a Eaton M90 blower and a 600 CFM carb, worked great, loads of low end, but, there's no room for a pulley to run the blower from a separate belt(an electric fan may make enough room.)
I also made up a 4-71 blower setup, it's going to go on a street rod if I ever get a round tuit, tested it on my truck, but didn't drive it on the road, just a few runs down a runway.
I'was running a MAF MPFI EFI system off of a 96 F250, a bit of work to install and get it working correctly, but, well worth the effort, the difference in driveability is phenomenal. But, it didn't like my cam, so I'm back to the stock 1bbl...
Edelbrock(Both it and the H-M piece are out of production and fairly rare)
Hedman - A very high quality unit, installs as the instructions say, have to drop the starter to get the front collector by, comes complete with all required new parts(manifold gasket, collector gaskets, reducers, all required new bolts.)