Which Cam And Lifters To Go With...

It is my opinion that the cam is the most important part of the build.
You have a budget of up to $300... for another $30 you could have a custom cam ground for your exact needs.
My Dad's car has the same heads, same intake (essentially, it's a tue gt-40, tubular one, but same flow as Explorer) stock shortblock stock lifters, custom cam from Buddy Rawls. It has amazing TQ from right off idle and pulls to 6k rpm silky smooth. I forget the exact numbers but IIRC it makes handy 340tq all day. HP was right handy 300... 290-310 don't remember but right there. Again, excellent drivability, pulls from off idle all the way through with no hicuups.
Those numbers are not typically associated with that head/intake combo (especially tq), which speaks volumes to the cam performance.

Again, take a brown bag lunch to work for a week and save up the extra $30... than contact Buddy Rawls.
As a testament to what a proper cam can do for "crappy" heads, I make 368rwhp with stock iron heads and a cam from Buddy Rawls.
Don't short yourself on the brains of the combo.

Contact comp cams,Lunati,or bullet cams. You can fill out their online forms and they will email or call you with a recommendation. A comp cam 270 HR is a decent ots option. A trick flow stage 1 would work also. The custom route is the best option and well worth the extra cash/time. Check out flowtechinductions.com. The owner's name is Ed and he has literally done 1000's of cams for your similiar setup.

Buddy used to have the most informative camshaft site on the planet, but I see it is no longer up and running. Hmm.

I understand you concerns. He is good people... I could go on and on, but, again, understand your predicament... so...
I've pm'd you a cam card... founding members gotta stick together... now, that was designed around 1-3/4" long tubes, but would guess it's still better than any off the shelf outfit.

If you want a torque-y motor with great drivabilty that pulls hard from off idle through 6000... that's your ticket... sounds really nice too.