The classic API VP312 is made by Classic API of Illinois. available for purchase as a kit or assembled, it emulates the API 312 style microphone preamp in a 500 series modular rack. When Jeff designed this excellent preamp, he added a few resistors for transformer loading, but I think the circuit is for the most part a spot on replication of the original 312 circuit.
It has 60db of gain. We have ours loaded with JE990 Op amps which are of the typical 2520 op amp footprint. It has a 2503 output transformer and you can use a Cinimag transformer if you want. The DI Circuit is great for recording bass in the control room. We have tried GAR2520 op amps for an enhanced low end distortion.