Factory specs are probably low, I haven't got the factory specs but would start with 10 * to 12* BTDC with out vac connected and make sure that it didn't ping. You shouldn't need to alter this unless you have removed the distributor because it is electronic and shouldn't alter.
Having said that I did check my '79 LRE because of a problem and it was set at 27* BTDC which is way too much.