I just installed a 351W with the MSD billet dist. It does fit even with the extra soundproofing and SS firewall. It is tight but enought to allow for easy removal and timing ajustments even with 8.5mm wires.
While you are at it, take a look at the shortened waterpump from Ford Racing. The shaft is 1.5 inches shorter then stock. The H20 shaft and pulley are the main components which egress into the passenger compartment. I purchased a stock pump but just ordered the shorter version.
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