With the engine being non standard it'll be a bit tricky to decide what the total advance should be and at what rev limit. For what it's worth, my engine has a total advance of around 34* at 3500rpm but then it's a plodder. The 2 litre 911 had a maximum advance of 35* at 6000 revs but that was a screamer.... I always found revving it up to 6k in the garage with the hand break on a bit daunting.
All you can do is look at the data for engines that you think may be similar to yours and have a play around. By the looks of it, the 123 Tune would be ideal for this type of experimenting.
I've found getting the timing spot on for both the 911 and 356 gave more power and made everything so much smoother. Well worth the tinkering.