Timing question on my auto car..??

I have a 400 swapped in so the 301 sticker don't mean much.What should I set my timing to on my 400..its a 77 to 78 engine I think and do I set it in drive with the vac advance line blocked off at a certain rpm like 650 or something..I do have a book that shows numbers like 16 degrees btdc for the 78 400 at around that rpm or do I set timing with the car in park or neutral.I don't have a park brake so will have to have someone hold the brakes to set it in drive while I time it.
also any advice on setting advance curves on basically stock 400. my timing light is pretty sophisticated.it better be it was like 100 US>

You set it in park with the engine warm and vacuum advance unhooked and plugged. With low compression, I can understand why 16 BTDC would be spec'd. But they would also put a distributor on those engines without a lot of mechanical advance. So total timing at high rpm would be around 36-38.

14-16 would be a good place to start, but check total at over 3500. If it gets over about 38, you are going to have to limit total timing. If you look at distributor advance mechanism, you will see that a rod rides inside a slot. If you shorten the slot by brazing it, you limit total timing. Or you can put a bushing on the rod and accomplish the same thing. Excessive total timing will cost you power.