Here are the motors listed in the R/C Unlimited rulebook:
i. NEU 1527 1.5Y 850KV
ii. HET Typhoon 700-98 840KV
iii. Turnigy SK3-3994 850KV
iv. TP 4040 10Y 830KV
As far as ESCs and batter packs:
Electronic Speed Controls (ESC)
a. Any ESC may be used as long as it is rated to a minimum 130 Amps and rated to handle a
minimum of 8s battery configuration.
b. Anti-spark resistors are advised on all speed controllers.
Batteries
a. A maximum capacity of 8S Lithium Polymer (LiPo) batteries are approved. The maximum total
mAH capacity of the battery pack(s) will not exceed 6000 mAH. Only LiPo batteries with a cell
rating of 4.20 or less volts per cell are approved.
b. LiHV batteries with per cell capacities to 4.35 volts or higher are not approved.
c. Manufacturer’s minimum discharge of 30C constant shall be allowed.
These are what are allowed in R/C Unlimiteds. Throw in a hard or flex shaft with a 57mm prop and you're good to go