Did you measure your rod journals on the crank?
Just because the main journals were .010 undersized doesn't mean the rods had to be also. The original part numbers you quote (CB 926P CB 962)are standard size for the rod bearings according to a web search.
The bearings you got from Summit CB-927 HN-10 are .010 undersize.
That would definitely keep you from moving the rod once you had torqued down the rod bolts.
Jake
PANTERA INTERNATIONAL
A DE TOMASO CAR CLUB
Presents the De Tomaso Forums
The On-Line Meeting Place for De Tomaso Owners and Enthusiasts From Around the World
Clicking on the banner will take you to the sponsor's website.