Just for my own edification, because we are talking about numerous manifolds here, is the 440-3 the new one that Indy sells on their website?? That is the route I have chosen, I don’t want to use a spacer. Thanks 440-2 RB 4150 440-3 RB 4500 440-3X RB 4500 taller and extra plenum volume. 440-3 has been for sale for a while, early ones seemed to be a plunge cut -2, later ones a dedicated cast 4500. All are single plane, part #'s seem to have changed on the new website though 
'74 Challenger..9.46 @ 145.9 1/4, 6.001 @ 118 1/8 so far. 4023lb !!! # N/A, Marsh performance 655ci, Indy Maxx, T/R, Indy 600-13 X's, Street legal, pump gas, full interior, Cal-Tracs, mufflers, 3:73's and real 10.5 radials.
9.51 @ 142.4 1/4, 6.003 @ 114 1/8 with our old mule KB, 572-13, 580 wedge.
RHD '68 Barracuda Fastback 323ci street/strip. Best ET 13.88 @ 99.03
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