Silvertone 1335

Hi Skip,

I have aquired a Silvertone 1335 (15" speaker version). It is all original besides a cap job, 3 prong etc. It has a great sizzle to it and is very responsive. Curious if you have any experience with this amp. It could be tamed a bit like most guitar amps. It's pretty loud before it gets to feedback so overall volume isn't a problem at the moment. I'm curious about which, if any, tube swaps that may exist that will give me some different tone. Options, ya know? I ask too because the tube layout is far different than I am used to. This amp is a fair bit older than my others. 

Thoughts?

SJ