Sorry to say that a Dutra casting will not clear the standard starter, when it is installed with a later "RG" 727 automatic trans with the "high mount" starter, using the 727's common 143 tooth ring gear size.
As others have commented, the Dutra casting, machined to service the rear 3 cylinders, is a tight fit, when used with the 122 tooth (904) high starter location but the Dutra exhaust manifold becomes direct interference, when the starter moves up & outward, as it does on the high mount 143 tooth ring gear, RG727 auto trans.
(a 727 w/ a Slant 6 bell housing, not the low starter adaptor plate set-up)
A modified (capped-off) factory manifold combined with a Dutra front manifold works just fine with the RG727... and you get to keep your choke and intake heating.
But, if you really want that "clean look" of the dual exhaust pipes, coming out from under the intake manifold there may-be some newer starters that can be made ("clocked") to clear that high mount 143 tooth RG 727 starter location, with a rear Dutra manifold.
Another option is to make a special modified factory exhaust manifold, with-out the intake heat box,
DD
