L76 to LS3 conversion

I have a 2009 G8 GT (L76 6.0) that I have DOD deleted and installed a stock LS3 cam. Essentially this gives me a 6.0 liter LS3, with 3.3% less displacement than a "real" one. I know that the MAF and injectors are the same between a GXP (LS3) and a GT (L76). The throttle body does show a different number. Is it safe or wise to simply copy the timing and fuel-related tables from a stock GXP file to my GT tune to create a baseline tune for my Frankenstein? I believe this would give me a HUGE head start toward finishing the tune, if doing it this way is possible or advisable. BTW, I do not have access to a dyno, so I see this as a way to get similar-to-stock-LS3 performance with proven stock durability. The LS3 stock is about a 50 HP gain over the stock L76. FYI the ECM is an E38.

Anyone out there actually done this before?

Thanks in advance,
Pat

Still need to tune it as you would normally, conservative spark until the fuelling is dialled in with a wide band and then see how much spark makes it happy and doesn't knock.
While the LS3 cam is better, the difference between a an L76 and an LS3 is about more than just the 3.3% capacity, the LS3 has a larger bore size which reduces shrouding of the valves giving the engine better air flow characteristics.

Xjas, I appreciate the guidance. Makes total sense.

Thanks,
Pat