i just saw in the chiltons manual for my truck that it is recommended not to exceed 35 lbs/hp for towing as a general rule...

example - say your truck, you and passengers, boat and trailer all together weigh 3500 lbs, then 100 hp or more should be within limits with no modifications

it went on to talk about changing gear ratios and adding a transmission and/or oil cooler to enable towing heavier loads without the extra wear on the engine and parts, if someone would be interested in messing around with that

as far as a V-8 goes, i wouldn't think that you'd ever need one for a drift boat...i pull an 18' alumaweld with my little 4.0L ranger and that is all within the weight limit for power/towing, etc.