Right now, I'm assuming you have the original 1967 289? If so, it will have rail rockers... or rockers that have two little fingers at the tip that straddle the valve stem to keep them centered. Updating the heads will require a few, small changes. I believe the GT40P heads are the ones that came on Explorers. They have a revised spark plug location, and usually require special headers. If you go with an aftermarket head, I would avoid the Chinese stuff. Usually more problems with them than the others. Edelbrock heads are made in USA, and have a lot more Quality Control. The offer a very inexpensive choice that would work just fine on your car.
You really need the full COMBINATION to make your car 'right'. I would install an Edelbrock 4bbl, Performer RPM intake, you cam is probably fine, the low cost Edelbrock heads, headers and at least a 2-1/4" exhaust.
The Edelbrock carb is nice, in the fact that it is easy to tune, provided great throttle response, and gets better fuel mileage than a Holley. The old Performer 289 intake is 50 year old design that is okay for putting a 4bbl on an otherwise stock engine, but the Performer RPM is better in every way. It's also not that expensive. The heads are the worst bottleneck on the small block Ford, and should be upgraded every build. Headers allow the heads to do their magic, and a decent sized exhaust allows all the other parts to do their thing.
These Edelbrock E-Street heads are set up for a flat tappet cam, and are the least expensive heads Edelbrock makes for the SBF. https://www.summitracing.com/parts/e...view/make/ford
They use guide plates, which will require hardened pushrods, and you'll need different rockers. Scorpion makes an affordable high quality aluminum full roller rocker. You can also get the Comp Cams roller tip rockers if space under the valve cover is a concern. Either way, it's advisable to adjust pushrod length to get good rocker geometry.
I'd either keep it stock, or do the whole combination. Doing only part will leave a bottleneck somewhere, and it won't run as well as you hope. If you're having to pay others to do it all, have an engine shop do the entire engine. Most regular automotive/restoration shops don't know the ins/outs of old Ford engines.