All I'm looking for is a good used loco that will pull my short trains without any problems.
Ok, I am on the same page now.
Yes there are many good options. As at least two other folks have mentioned an Athearn "super power" F unit. It has an extra weight over the motor that gives it some really good traction. I am guessing even an Athearn blue box GP7 would work. Lots of pulling power for a hood unit.
I believe a Life Like Proto-1000 FA might be a good option. Every time I pick mine up I am amazed at it's "heft".
I also had an Atlas (yellow box) SD24 that could pull 45 cars (not on 18" curves but up a 1.5% grade), that I could recommend.
In general I would say almost anything from the main non-toy train set brands after 1984 and before sound and DCC (1995?) would be candidates for a 4x8 layout. I say before sound and DCC because manufacturers started taking out weight to make room for speakers and circuit boards. Non-toy train main brands being Athearn, Atlas, Bowser, Genesis, Inter-Mountain, Kato, Proto-1000, Proto-2000, Spectrum, Stewart, and um um probably missing a couple.
Toy train brands being AHM, Bachmann, IHC, Industrial, Lifelike, Mantua, Marx, Mehano, Rivarossi, Tyco