As others (including myself) have repeatedly stated, the solid mount's original use was as a PS motor mount on a Hummer H3. The GM part number is 25847739. This same part number will fit both sides. I bought two, and a trans mount, with the intention of replacing them all. But I've only replaced the DS so far (original was ripped almost in half).
Things may have changed. But when I tried to get the parts, they were on national backorder. I had to go through three places to get them ordered. I finally found an online dealer that got them to me. But I had to lie and give them a VIN from an H3 before they'd take the order.
Replacing the DS mount took me about 2 hours. You can find details on the swap elsewhere in this thread, when I did it not long ago. The PS looks to be quite a bit more challenging.
The solid mount does transmit more vibration at idle. It's noticeable on my truck. But I don't know if that's normal, or indicative of some maintenance I need to do. I'm working through that process now. Even if it turns out to be inevitable, I'll take it to avoid replacing the mount again.