love the trailer - really really well thought out.
You weren't wrong to go with a 16v Sidekick swap, even tho' I've done both a 1.9td (27mpg at 65mph w/35's) and a 1.9 TDI-m, I don't tell everyone the diesel is the only way to go. I thnk you have to love the diesel concept to love the conversion, while the gas swap is pretty straight forward to use. I also would have reservations about the stock Samurai transmission holding up to a diesel pulling a trailer. My trans would be be too hot to touch after a 1 hour 65mph commute. The diesel makes so much torque you could pull long uphill grades with your trailer at 70, and it's so much fun it's hard not to.
That's the other plus of the TDI or td - boost makes up for altitude, you get about the same power at 10k feet as at sea level. If you find the 16v isn't doing it for you, later, the TDI will do it, but you'll want a Toyota transmission to go with the power you are adding - it's it's not horsepower I mean, it's the torque - the stock 1.9 tdi made 150 ft lbs at 1500 rpm, and it's soooo easy to get a lot more....