ld340 manifold

Grain-man
An LD-340 manifold will take a standard Mopar T-stat housing, Unless it has been modified. Two bolt holes on either side of the housing is correct, I think the bolts are 3/8, or 7/16 in. It sounds like one of the bolt holes has a repair to it. It could be a Heli-coil. The heli-coil should be tight,so as to hold the bolt good. Make sure it is and also make sure the T-stat housing face on the manifold is flat, use a steel rule for a straight edge,if it needs fileing, leave the surface a little rough so as to hold the gasket better, but make sure it is flat.
An LD-340 is a good maniflod, wish they still made them.
Dave C.