hey nate,
it's been a while, but i'll tell you what i recall. i tried to send you pix via e-mail, but all my attempts bounced back to me. my 66 was one of the first magnums actually. i was still able to eek a lot better performance out of it though. if you're not playing records right now, one tweek that's worth while is removing the tubes from the the phono stage. also get rid of those cheap gold plated tube sockets. i replaced them with silver audio note sockets and was amazed at how much better they sounded. i replaced all the signal wire with 5n's silver in teflon tubing. all power supply caps were replaced with panasonic ce caps. coupling caps were replaced with auricaps. the power supply cap inside the preamp was doubled (you'd have to see pic) also using the panasonic ce cap. the iec on the power supply was replaced with a croyed silver furutech. the chassis was damped with verra star copper sheets. out of all the tubes i evaluated, my two favorites were the amperex orange globes and the mullards. i had a beautiful set of perfectly matched 5814a's from a holland radar station, but i never got the chance to listen to them. i also used herbie's hal-o tube dampers, wooden knobs (thingamaknobs), wood top loading weight and isolation.
it's a nice little pre with a short signal path. i had a 99 magnum here and preferred the 66 magnum side by side. over-all the 66 was less veiled, less colored and more quiet imho.
if i can recall more details, i'll let you know.
best, scott