So... stock headed 318s have torque and like to rev over 5000 RPM? LOL
First, you're comparing a modified 318 to a particularly bad version of the stock 5.0. There are many many many 318s in stock form that have wet dreams about running in the 15s.
Second, the 85 5.0 is not typical of the 5.0 Mustangs at all. Especially the TBI LX model. 87-up gets better heads, better cam, factory dual exhaust, etc. With a stock 64cc head, the Mustang gets 9-9.25:1 compression. The 318 gets what? 7.8:1?
Further, I didn't say the Explorers were fast, I said the ones equipped with GT-40P cylinder heads have great heads. Mopars don't have an equivalent cylinder head lying around in junkyards, and even if the 308 was close, they're all cracked anyway.
Example:
A buddys Mustang 92 LX coupe that I helped build: bone stock GT-40P Explorer long block with mustang STOCK camshaft, EFI, etc, 11.90s @ 112mph. $700 factory junkyard engine! Makes 290+ rwhp, 330 ft-lbs of torque.
This is where I got the idea to build my junkyard 5.9 Magnum that's in the dart. The magnum has cost more, and has an aftermarket cam and cylinder heads, but makes about 40 more rwhp than his 5.0 and even more torque. Plus its cooler!
I have had many Mustangs also. None of them, even in their most basic bolt on stages would have ever been beaten by a car running 13.45.
A 5.0 5-speed with gear, slicks and underdrive pulleys will run high 12s if you can drive. My stock blocked 5.0 with a Zex kit went 11.20s.
HOWEVER:
I can see the appeal of building a 318. They have been derided for so long its fun to turn it into something, but $$/hp its a more expensive and trickier deal than building a Ford 5.0, simply because the 318 is compression and cylinder head handicapped in a way that the 302 is not. Thats without even getting into the hydraulic roller vs. flat tappet thing...