Just my opinion,but if the stock negine isn't enough to flip your trigger,why not try a 270 or 302 GMC six,or a Chevy 292. Granted,those aren't fire-breathers out of the box,but you can still get enough accessories (intake set ups,headers,cams,electronic ignitions etc.) to help them run with the small block Chevies,especially when it gets down to the loooonnnng grades with a good load on. By nature,the six pulls best in the 1,800 to 2,500 rpm range,and they hold their mud when lugged steady in this range,where most all smallblocks start losing ground as soon as you load them like that.
Plus,the six will be a lot easier to install and cool.
