>> will it allow other vehicles which fit the "formula"?

Anything that fits the formula. It's actually easier to make cars competitive in these classes as they will use SIRs and weight to equalize them.

Here are the engine rules, the rest are in your new SCCA GCR that you have or will have shortly:

D. Engine

1. Alternate engines may be used, given that the manufacturer of the vehicle and engine are the same (e.g. Acura engine installed into a Honda auto). Replacement engines shall have the same number of cylinders/rotors as the original.

2. The connecting rods and crankshaft must be stock OEM parts for the specific engine, but may be tooled enough to achieve balance. The standard weight reduction allowance for balancing of the crankshaft is 0.5 lbs. The standard weight reduction allowance for the balancing of the reciprocating assembly is 15 grams.

3. Blocks may be sleeved to repair cylinder walls.

4. Rocker arms, lifters, followers, pushrods, valve springs, keepers, retainers, guides, seats, and valves are free, TITANIUM is NOT permitted, except for the retainers. The head may be machined to fit valvetrain components.

5. Valve lift is limited to .600". Camshafts and timing is free.

6. Cars produced with an electronic throttle body may use the OEM electronic throttle body. The OEM electronic throttle body may be converted to manual actuation and the actuation cam on a manual throttle body may be changed to alter the opening/closing rate of the butterfly

7. The ignition system components may be replaced freely provided that the type of ignition remains the same as stock.

8. Engine calibration (spark and fuel) is free. A programmable ECU is permitted. The RPM limit set within the engine management system shall be the same for all gears (i.e. 1st gear shall not have a lower RPM limit than 2nd-6th gears).

9. Fuel injector(s) and fuel rail(s) must maintain the original number and mounting location(s), but are otherwise free. Fuel pumps and fuel filters are free in type, size and number.

10. The location and type of the fuel pressure regulator(s) are free provided they are mounted within the engine compartment.

11. The ring gear diameter must be the same as the production flywheel. Flywheels shall be ferrous metal, or aluminum, but are otherwise free. Titanium flywheels are not permitted. Clutch and pressure plate design is free.

12. Oil pan and oil pickup may be baffled, modified, or replaced to prevent surge. OEM oil pump may be modified, or replaced with an OEM-style oil pump. Cars using a wet-sump oil system shall safety wire the oil drain plug, or in some other way secure the oil drain plug, to prevent the plug from accidentally coming out.

13. Vents, breathers, and oil filters may be added, or substituted. All emission control devices may be removed and the resulting holes plugged.

14. Replacement gaskets and seals are free, including head gaskets. Replacement gaskets and seals must be made out of material(s) designed to seal the parts of an engine. Replacement gaskets and seals may not perform any other functions. Head gaskets may be used to adjust compression ratio.