The 1520 might work for you - but you'd be pushing it depending on your final weight and gearing. If the truck ends up being 18lbs and you try to gear for 60mph I would guess it wouldn't work too well. A 1717 would be better. But if that won't fit, your best motor would be a 1527:
http://www.offshoreelectrics.com/pro...u-1527&cat=117
If you have a 1520, you could try it and watch your temps. But if you need to buy one for $200 or more on eBay - I would probably pay a bit more and go with the 1527. My experience with the 1527 is in my 19lb truck geared for 50mph - it worked great, but on a hot day would go up to 160F or so (without a fan).