273 Cam Shaft Wear?

It doesn't look the greatest to me and if I were rebuilding the engine I'd would replace it. As for what to use I think you'll be ok with the larger of the 2 you listed but you would probably be better off with a XE252 comp cam. It's about the same size as the MTD-1 you listed but the lift profile is a little more aggressive (ramps up faster) so it'll make more torque and that's what you want with a small cubic inch engine. Here's a link to it on Summit's website so you can look at the specs

http://www.summitracing.com/parts/CCA-20-302-4/