E38 ECU ECM compatibility. HELP!

Alright straight to the point. I hope I can get some guidance from the tuning gurus in here

I have a 2008 g.m ly6, vvt, with ls3 intake/injectors/headers into my 69 camaro:yay: (
finally)
Totally new to tuning so please excuse my ignorance. I finally got to "scanning" the ecu....and it turns out i have an e38 ecu off an 2007 impala v6 serv#12597121 :doh:
(The fly by wire works when depressing the gas pedal, fuel pump come on)It came with the engine when I purchased it from the junk yard. i have HP tuners vcm suite. i have read that it can be overwritten? but since i am keeping the vvt, can this still work? or do i have to purchase another e38 ecu? If i can keep it, how do i go about overwriting it. Sorry for the 21 questions. Any help is always appreciated.