In my experience with multiple unibody based Ford cars, weld in subframe connectors that tie the torque box at the front rear leaf spring perch to the rear of the front frame rails near the toe boards absolutely make a difference in resisting chassis twist and improving vehicle stiffness.

As of today there’s one listed for sale on the other forum

https://www.fordfe.com/rare-dove-fe-427-hr-magnesium-1x4-spider-intake-t170278.html

My experience with lockers is that they like to coast a little bit, off the throttle, before making a turn, especially with a manual transmission. Coasting a little allows them to disengage fully so you don’t get the chatter that tries to shake the car/truck apart when trying to turn. I kind of like the soft ratcheting noise when making a tight part or off throttle turn. Lockers are cranky and take a little getting used to, especially with a manual transmission and in the rain, but once you learn the nuances, I love that when you jump on it it tries to go straight. I’ve used them in several daily driver type cars and trucks that got flogged regularly

Given that Mr. Jay Brown created and maintains this forum, I'd say the general consensus, and might I add decent thing to do, would be to 'send him a check'. It'll be a worthwhile investment into your library. 

PM sent

I swapped from a port matched F427 to a port matched RPM to a ported (collar removed from plenum, runners blended into plenum, runners opened up to MR port size at head and blended up into port) Streetmaster on a fairly mild 428 build a few years back. Combo was .040 428 with CJ style dished pistons, heavily ported C6AE-R heads with 2.09/1.66 valves, about 10.1 compression, mild Crower hydraulic cam with 220-228 @ .050", 112 LC, .540ish lift, Holley 780 VS carb, 1 3/4 inch primary tube headers into 2.5 inch duals, C6 auto with 2,200 rpm stall, 3.89 rear gears with a tall tire. Ran this in a 3,900lb 65 F-100 SWB truck.

With both the F427, then the RPM intake, it had gobs of power as soon as the converter stalled out, would blow the tires off pretty easy (too easy). I think the F427 and RPM were on par with each other for that build. Swapping to the Streetmaster, it lost about 1.5-inches of manifold vacuum at idle, and was noticeably softer below the converter stall, but above about 3,000 rpm, it came on hard, and according to my seat cushion, pulled much harder through the mid-range up to the shift point (about 5,500 rpm). I was able to control the tire spin better too, so I felt it was a win on my combo, for what I wanted. Cruise rpm with this combo was about 3,000 rpm at 70 mph, and I noticed no change in driveability or economy in this range. I did have to diddle with the power valves, jets, secondary spring and timing a bit between the two intakes. The Streetmaster worked best for me with a 4 hole spacer on top of an open spacer, where I ran the RPM with just a 4 hole spacer.

For my current 428 build, same truck, with more compression, Edelbrock heads, huge solid lifter cam, 3,000 stall converter and wide ratio gear set in the C6, I kept the Streetmaster and am pleased with it.

For your combo, given that you have more weight over the rear tires than my truck and likely traction will be improved, I'd probably go with the F427, for as others have said, it will look 'right' in that engine bay, and will be in the sweet spot for your driving range.

Brett

Back to the top again, some stuff sold, another round of price adjustments on what's left.

Thanks, Brett