6.1 cam swap. Big deal?

The PSI 1511 can be used with the old cages - or using a locater and shim

Running it without either will result in lower seat and open pressures...defeating the reason for the change - ...but the real concern is that the spring may move around on the pad.

You really need to get in touch with Chris from Modern Muscle on here...or contact Craig from Thitek..and ask them to ship the correct shims and locaters.