[1985 CCX]

NKB and D1Z427

Much appreciated but that one you have pictured is cast 5 bolt 289 unit.
Mine pictured in this thread is a cast iron 427 unit from FOMCO, much larger than 289 and also the same units used by Shelby American on 427 Comp Cars and the S/C.
My 289 has never had an issue after years of racing and most originals used stock Ford unit. Stock 289 FOMOCO units were alloy, the cast units for special purposes only, if they blew up on a normal occasion Ford attorney's would have made them cast iron in the day. All 1965, 1966 and forward up to the Fox-body as I know Mustangs were std alloy units as the explosion hazard was very exclusive to racing. Stock hp cars, as mine are have a very very low risk in this area as I understand.
Assume same for the two 427 I have, its a rare occasion to lose a flywheel. Particularly with stock Hp and dragracing avoidance.
Also, a period cast 289 unit may protect but if your a safety concerned a newly stamped Lakewood may work and protect much better.
My HiTech 427 uses Lakewood unit.