I am going to start reloading and was planning on buying a lee breech lock challenger kit. I was wondering if rcbs dies will thread into this press? also any info on this kit would be appreciated.

Yes the RCBS dies will work with the Lee Breech Lock system, they are the standard 7/8-14 thread.

Is there a reason for preferring an aluminum frame press to cast iron?

I have a low budget but if you know of a cheap cast iron frame kit I would like to know

the lee will work just fine.i have loaded thousands on mine without a problem.

elmo729 - "I have a low budget but if you know of a cheap cast iron frame kit I would like to know."

The Lee Classic Cast press is iron/steel and is as strong as any, stronger than some big names, but sells for much less than any competitor. It also has several design features that place it ahead of all its single stage competion except the Bonanza Coax and Redding Ultramag, both coming at substantual increase in cost for little real gain. IMHO.