360 does not seem to be making power and is slow in the 1/8. Need help and/or suggestions

So do you have a ET slip you can show?
1/8 mile right?
Does your track have a half track reading (330 foot)

Are you removing the vac advance when your checking initial timing. What is it at idle? How much rpm does it take to get full mechanical advance? What mechanical advance springs did you say you had in the distributor? How much advance is in the distributor. In other words if you set the initial at 20 degrees, how many degrees will it advance to??????

With out having any of these answer...........I say you need to twist that distributor base in a more advanced direction.