I’d like to verify that a 5R4G Rectifiier can replace a 5U4G.  This is for a Torii Mk4.  I thought I had seen in a post here that it could, but couldn’t find it again.  Thanks.

It will probably work fine, IMO. The 5R4 is in between the 5U4 and 5Y3 (or type 80) in the rectifier hierarchy, so if you'd use a 5Y3 in your amp then a 5R4 will be fine. The concern is that is it only rated for a 4 uF power supply capacitor. But I've used them in in my UFOs with no problem and I fell like the maximum current rating is very high and in general old stock rectifiers are really robust so I wouldn't hesitate. But the JMO/FWIW/YMMV.

Just what I needed to know.  Thank you.