At 75 -80 mph I dont think I would want to jamb the breaks on or have to do any evasive maneuvers...lol. Wonder why the dually would squat so much?

what brand boat trailer do you have,surge or electric over hydraulic brakes?

The difference has to be in the trailer. I have a 2500 HD crew cab with the 8.1, gets around 7 mpg towing. It has plenty of power but the trailer doesnt follow very well. It is a pacific trailer that was made for the boat.

I trailer my 38 with a 2000 Ford F250 Crew Cab with single axle and it pulls very nicely. I can cruise all day at 70 mph and get about 10 - 11 mpg (thanks to the old 7.3L with some after market items). Very little squat and no issues with cross winds or passing semi's. The trailer is a Heritage triple axle and has outstanding brakes.

Pulling a 38 over a 34 you will not even notice a differance. I pulled mine with a 2005 crew cab duramax for 3 years through the hills and turns of the Ozarks all the time and NEVER had any issues with it at all. I now own a ext cab 6.0 to pull it when I need to, but for the past 2 seasons it was on a lift in the Ozarks. You do NOT need a dually, unless you actually just want it. Mine sits on a Integrity trailer and overall length is 45 ft. I hold a CDL and when I use to drive pulled tandem trailers so I do have experience with pulling things. As for brakes I have serge, and again if set up correctly you will have no issues stopping or making fast moves. Again if you have ever drivin to Lake of the Ozarks you would understand taking some fun curves at 70 MPH and people pulling out in front of you or deciding to stop and turn right in front of you.

I also have friend with boats just as big or even bigger and non of them own a dully. A 42 Outerlimits with a crew cab F-250. Or a crew cab 6.0 chevy for a 35 Cig.

Good luck in what you get

I am eyeballing a 2002 Vyper that is listed in the classifieds which has 496's but really wishing it had 500's.
I think a 3/4 ton diesel would be enough truck.

Good day, i have a 2000 vyper with the 500 efi blue engines running 30 pitch labbed props, the best it runs on gps is 78 mph at 5200 rpm

as you can see not much different in speeds ,and if you leave the 496s alone/stock they are bullet proof with less maintance then the 500s

It is very hard to leave well enough alone though, but your right!!

I have a 99 34Vyper with 500 EFI's 4 blade 30 pitch not labbed props, do you think that would cause prop wash on take off. I have alot of issues with take off in big water.