Race numbers & names...

[gn7]

SS, pretty much a spec engine. 440 max cubic inches big block Chevy only
18ft max length flat bottom approx. 1850 lbs with driver
Specified manufacture for piston, manifold, and heads as manufactured zero modifications
spec gasoline
Single Carb limited by the throttle blade size but open to any modification.
Flat tappet camshaft,
steel connecting rods of the stock length.
Max 4.320 bore, stock 3.766 stroke Limited manufactures allowed for crankshaft
wet sump oil system with oil pump in the pan

Pro Stock:
500 cubic inches, any make production type, iron block, aftermarket OK, no overhead camshaft
Unlimited modifications unlimited carburation or fuel injection, no blowers
methanol alcohol or any gasoline
18 max length flat bottom 1850 lbs minimum weight with driver

K boat
open cockpit: 470 cubic inch limit 8-71 blower
capsuled: unlimited inches unlimited blower
any engine production type, iron block, no overhead camshaft
Unlimited engine modification
18ft flat with special rules for boats up to 21 ft. Minimum weight 2250 lbs. with driver for 18ft, 2400 for 21ft hull

GN
470 cubes for blown engines 525 cubes for unblown engines
any make engine production type, iron block, aftermarket OK
8-71 blower with 3% limited to 3% overdrive
any carburation or injection
unlimited engine modification any oil system
any gasoline or E85
25 ft max, no weight requirement but most weigh in the excess 2500 lbs no driver

All of the above must have rear engine driven thru a v drive to a prop under the boat.

APBA Crackerbox
Probably get some of this wrong
13.5 to 15.5 length with some pretty strict dimensions laidout in the rule book
Minimum weight???
314 cubes iron block based on production engine. aftermarket OK
No overhead camshaft
650 cfm carb with virtually no modifications allowed
unlimited engine modifications
direct drive, no v drive or gear box
gasoline
Note: there is a alternative 275 cube engine that is allowed methanol and fuel injection, but nobody I know of uses the alternative engine today.

Cracker Pro (Lucas Races)
Pretty much the same as above. You would have to ask Andrew about any differences.

EDIT for minimum weight corrections