Some extra side clearance is harmless, but the entire width difference (1.430" - .990" = .440") will allow the rod to wander around too much IMHO.
The width of the journal can be reduced as part of the grinding operation to create a shoulder matching the original GMC area.
The pistons can be constructed with the pin bosses very close to the rod eye width (eye + .010") to guide the rod from overhead.
As long as the tangs, dowels blah in the bearing are secure in the rod as usual it should work.
