X2 These were commonly used.
Like has been said already, unless you are building a factory fresh build, you can use what ever engine you would like.
The 3406 in the snap kits are not “B” motors. There is a little difference in the pump, front cover and the compressor mounting on the 3406B, but Gary Wallace offers the “B” motor as well.
Paystars often used 3208 Cats as well, but I am not sure how late those were used.