I'm sure a 390 is a decent engine when built right......however.....I would never put that into something as small as a Maverick or a Mustang. There'd be oversteer problems like a BIG dog when cornering/ on sharp curves. I test drove an S code Mustang once when I was younger and happened to own a 351W powered 67 Stang at the time. There was a STARK difference in the braking and turning characteristics. Way too much weight up front for such a little/ light car and not enough performance gain to justify it IMO. Just my
I had a 390 in Galaxie Hardtop, late 60's early 70s', 4 sp. toploader, 457 lock rear used the car specially for racing. It had alum intake, hyd, cam & iron heads. Back-in-the-day ran mid-high 13 second 1320's. Engine had lots of torque. I would not put in a Maverick unless, alum heads/intake and tower/mod's or removal. I do believe, as others have stated, better suited in larger heavier vehicles. Cost of building one compared to SBF's would dig much deeper in checkbook. But, if building mostly stock for a street cruiser in larger vehicle -- make sense -- If for no other reason than being different from the masses.
It's kinda like comparing a boss 302 against the boss 429. Put them on a oval track the 302 will win. Stick them on a straight away. The 302 will get a head off the line but the 429 will win in the end.
390 has mostly played second fiddle to 406 & 427, performance depends on year, '66-'69 heads suck. The '61-65 heads were far better, was a 401HP version in '61. Std 428 heads are same as late 390. The 428CJ head is light years over late 390, those are patterned after 427. For this forum it's mostly irrelevant, not gonna fit without major surgery & core 427 & 428CJ sell for more than most Mav/Comets.