I've got a 383 SBC with an LS1B (411). There are a LOT of modifications, including TPI, 11:1 compression, headers, port matching on the intake and a high-lift cam (Lunati 20080720 w/ 1:1.6 rockers). The transmission is a 4L80E, with a 3.08:1 rear and 26.9" tall tires, all in a 3800 Lb. car.
Someone posted a tune for a '91 'vette with TPI (from Yellow05C6 here), but that has 16.9 degrees of initial timing, and I think that's too much for this engine/car.
I know that I have to create a spark table for this, as the LS1 table is unlikely to work properly. How do people do this from scratch?
I'm thinking that I can use six values from distributor tuning (Initial advance, Total mechanical advance, Mechanical advance start, Mechanical advance done, Total vacuum advance and Vacuum advance in by), and use the VE table to get an acceptable starting point. Does this make sense?
EDIT:
I finished the tool, cleaned it up and created some documentation. Everything is attached to this post. The ZIP file contains some sample data derived from the "Stock '91 Vette_0000.ctz" file referenced above.