I have a vintage 1967 Silvertone 1465 head and cabinet in nearly mint condition with all 6 original speakers.  It is stated to be a 150 watt amp with two channels of 75 watts each.  I've had it since about 1982 and I'm doing some work on the head.  I have the schematic and owners manual, which indicates that there are two main output power transistors mounted on heatsinks and one lower power transistor mounted on the main board.  The transistors are identified using Sears part numbers, and there is no reliable cross reference.  I'm wondering if anyone has replaced the power transistors in a Silvertone 1465 before.  The two higher power transistors on the heat sinks are labeled 9158.  From reading other online discussions, I've deducted that these can be replaced by NPN MJ15015 transistors.  However, I'm not sure what the single lower power transistor (labeled 3155) should be replaced with.  I've seen smaller Sears amps that use 3155s as their main output power transistors.  I wonder if the 3155 is equivalent to a 2N3055 NPN transistor.  I'd welcome any suggestions or commentary.