I would tread softly toward the 1969 4.00" crankshaft. I've seen just enough of those crack and fail to avoid them. Not trying to put a big black cloud over anyone's 428 build but over the years I've encountered several of those cranks that were either cracked or broken. One was in an engine I bought and put it in the Ventura. The crank ended up being cracked and took out the thrust bearing.
During my search for a replacement I found several others cracked or not serviceable and my crank grinder told me to go another direction. I ended up getting an earlier crank with a different casting number and it was fine and survived may years of abuse until I replaced that engine with a 455 back in 2000.
That was quite a few years ago but during my research I found different casting numbers for 421/428 cranks. Some early were Arma-Steel, then they used a casting from 67-69, then another casting in 1969 with a different part number. I'm pretty sure all of the bad ones came from 1960 360hp engines, but they may have used that casting in other. Anyhow, it was the later one that we found issues with.........FWIW........Cliff
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https://cliffshighperformance.com/
73 Ventura, SOLD 455, 3740lbs, 11.30's at 120mph, 1977 Pontiac Q-jet, HO intake, HEI, 10" converter, 3.42 gears, DOT's, 7.20's at 96mph and still WAY under the roll bar rule. Best ET to date 7.18 at 97MPH (1/8th mile),
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