New RVer!1976 Barth with about 102,000 miles.
Running rough ... replaced plugs, wires, cap and rotor ... still runs rough ...
How do you access timing marks to set the distrib uter and what is the best approach to adjusting idle speed?
Any/all suggestions/advice will be appreciated!
Brakes: any advice on bleeding or do I just open a bleeder and keep pumping and filling and then go to another bleeder and repeat until all bleeders have new fluid flowing?

The distributor is totally mechanical so you need to replace the points as well. The points will need to be gapped to achieve proper dwell. I am a proponent of leaving the functioning condenser in place rather than relying on the new one to work. While doing all this shake the rotor to see if the shaft bushings are worn then rotate the rotor to check if the advance springs are frozen, gone rusted etc.
If the bushings are good and the advance operates properly there are electronic conversions that will preclude many of the problems of the point system. In fact you could change to an electronic ignition system for probably about the same price, check ebay for an electronic dist. for a 454.

quote:

still runs rough

Check all vacuum lines...leaks will cause that too.

Maybe the timing/firing order is off...

1 - 8 - 4 - 3 - 6 - 5 - 7 - 2

The timing marks are in two places, the normal at the upper right side of the engine (which you can't reach on the P-30 chassis) and the lower right approximately even with the power steering pump. For this one you use plug number 8, not number 1, the normal plug. The Motrohome Cevy Manual has pictures and directions on this process. Someone on this ste has the pages you need.