In case you didn't figure out the answer, no, you can't run a production engine in Special Construction "A" class.
P-P describes the frame and engine class. There is also a P-PP and P-PV for production pushrod and production vintage engine.
If you run anything other than a production frame at El Mirage it puts you in the "A" frame class.
There are no limits to engine modifications in gas "G", or fuel "F" engine class. A blower puts you in blown gas "BG" or blown gas "BF".
If you run a pushrod "P" or vintage engine class "V" there are modification restrictions, but then append the G, F, BG, or BF to the engine class.
"A" frame class is un-streamlined, APS is partially streamlined, S is for streamliners - a whole different construction.
And don't forget SC for sidecars and SCS for sidecar streamliners.
In the back of the rule book is a list of numerical codes that give the legal combinations. You have to put the numerical code on the entry form, so if there isn't one, you can't run it.