My 340 completed and dyno test run!

I bet they are Lunati 72337-16.

EDIT: I'm almost certain those have the be the lifters. They are the only street performance retrofit hydraulic roller lifters I can find that Lunati offers for SBM. Plus the price matches up pretty close to what I paid, and my builder gave me a fairly detailed breakdown on all labor costs and there's no charge for modifying the lifter bores or lifters. I also recall talking to him about this and the retrofit are supposed to be made for "drop-in and go", in most cases.