my 18rc went pretty hard and all it got was stock... then i ported/ polished the head and shaved it a bit it went alot harder then i pout a 34adm webber on it jetted down it went even harder again... so if youi have a 18rc thats in good condition it will go well it responds well with little mods... i dunno if it was just mine and had good luck from a stock one or not but my 18rc went preddy good stock... but yeah the 18rg goes alot harder and is a better engine for doing mods to... that if you get one with webbers in very good condition