It's going to depend on what's in the engine of course.
Assume its something close to factory, and the distributor is something like a Mopar Performance with vacuum advance or factory distributor, that's probably a good starting point.
After driving it that way for a while, if there is no pinging, you can try advancing it 2* and see how that goes.
Put a tach on it when setting timing. I'm assuming here idle 550-650 rpm. if its 6* BTDC at 850 - 950 rpm, then I think its a little low.
I'm also assuming its a magnetic pickup distributor.
If your brother installed a non-C.A.P. factory points distributor, then 10 to 12* around 600 rpm will prob put the curve in the right spot.
