Sun tach AA batteries? Conversion?

Today I hooked up my 50's sun tach to my pop's 12v 8 cyl transmitter and put a couple of old AA batteries in it. Sure enough it worked pretty good. Can I just install it and run AA batteries, or is that a no no? Would it burn out the transmitter or the head?

Also, I have a 12v 4 banger transmitter, I tried it and it works, but reads to high on my '47 flathead with stock dual point. Any way to change it over without paying outragous prices? Either with or without batteries. Thanks.