Lets spec out a roller cam for my LA 318

The 9.0 is the limiting factor. Any cam you put into it, bigger than the current one, will drop cylinder pressure.
155 ain't bad, and presupposes an ICA of around 52*. The next bigger cam may drop the pressure to 150, and the next to 145, and so on.By 145 it's gonna be kindof a dog, off the line, and you'll be needing a much bigger TC.
Each 5 psi pressure loss, is easy to feel from idle to perhaps 3000rpm;so,at typical speeds your 5th is gonna see.
Your auto should actually be an A998/A999, if so it will have ratios of 2.74-1.54-1.00. But if indeed an A904, then your tires and 3.55s suggest gearing of 8.6 mph per 1000 rpm in first gear. That calculates out to 43MPH at 5000 rpm. When it shifts the Rs will drop from that 5000 to 2950, so there better be some torque down there, if you want to continue. The 2.74 low gear will make this even worse. If you put too much cam into it, she'll have a tuff time climbing up outta this hole.
Of course the solution is only a convertor away.
So, it looks like with a 9/1 engine, you'll be limited to exactly one cam size bigger than you currently have.
Remind me again what cam is in it now?

IMHO , I suggest you keep the current cam,(or a similarly sized cam with more lift to go with your new headflow),get a bigger TC, and up the rear gears. This will get you waay more performance. It will be like a supercharger.
The next bigger cam might make a few hp more at say 4800rpm,which you can't get to until close to 40 mph,with a probable loss of torque at the factory stall, and continuing a declining loss until maybe 3000(guessing).
But a bigger TC will get you an instant punch off the line from mild to wild, depending on what you choose. Bigger gears will let the engine run thru each ratio quicker, and put down more average hp during the course of the run, and get your zero-to-whatever time, down.
Jus saying