Since I have a mess of alloy laying around I might as well start casting for my Lott for a cheap supply of bullets.

Does anyone have any mold reccomendations?

I have taken this avenue also.
the 500,450, and 405's in the lee moulds
The lyman 560 gc mould is on a group buy at the cast bullet site. I got mine on ebay and it is my favorite. water quenched or heat treated it is awsome!
I,m now doin the same thing with my 416 rigby and the 375 H&H
hth's

I use a custom mold FPGC from Ballisti-Cast the successors to H&G for my .458 AR. Bullet weighs 435 gr.

I use the Lee 500gr when I need coincidence of aiming and impact points with jacketed bullets. Rick Rose likes that bullet as well. We're pushing them to Lott velocities.

I cast in air cooled WW, size to 0.459" and use Carnauba Red lube. Little smoke and little to no fouling ... and it's CHEAP! Remember that you do not want these too hard, the big .458s will drive them hard enough to shatter on impact if they're too hard.

The Lee mold is not a wonderful tool, but it's cheap and can be replaced cheaply. Just understand that you're not getting an H&G class mold. I have NEIs in .366", Lyman in .375, Ballisti-Cast in .458 and .475 and Lee in .458. Getting an NEI .416 mold soon.

I have a large supply of Lyman #2 and 20-1. Which alloy would you recommend I start with?
How are the RCBS molds?

Go with the Lyman #2 ... 5% tin, 5% Antimony rather than 20:1 Lead:Tin.