Initial timing specs for 1975 400 small block

[Billhilly]

I finally got my truck on dual fuel (petrol/propane) and am having timing issues apparently...The PO put a 400sb out of a mid 70's truck in. Casting number is 330817. I'd really like to find what the OEM timing specs were, especially initial. My repair manual that covers the right era says 'look at the sticker under the hood'.... Helps alot!
One of you guys with a squarebody must have a 400sb in there. Or point me to the right place on the net. I can't see anything at this stage. Thanks!