When using a modification to incorporate an assignment of claims, should the name of the Assignee appear in Block 8 of the Standard Form 30 (SF30) or the name of the original contractor?

The "original contractor" is still the contractor, so that's what goes in Block 8, NAME AND ADDRESS OF CONTRACTOR. An assignee does not become a party to the contract in any way, and the assignment has no bearing on the contractor's obligation to perform/deliver.

Could you, by any chance, be thinking about incorporation of a novation agreement?

Yes, thanks.