Here are more results from my testing as well. I only tested a single PI, but it seems they both run at 266 mhz.
I tested these firmwares: 252 mhz (1MB SAMS), 260 mhz (2 MB SAMS), and 266 mhz (1 MB SAMS)
These all passed the SAMS burn-in (3+ passes) on both the silver TI and the beige TI. I tested using the onboard cart functionality (without FG).
I hadn't mentioned it before, but I have another beige TI. It came with a Mitsumi keyboard, which isn't working. I did a keyboard swap so I could do some testing using the PI Pico. The TI is a QI model (non v2.2 1981 ROM), so it has potentially some differences in the motherboard timings.
I had to test with the FinalGROM on the QI TI because the Pico onboard cart would not work. I was able to choose the cartridge but after the reset, the cartridge would not show as an option.
In any case, I tested using the same firmwares as the other two TIs. All passed the SAMS test.
I will try to test the 264 mhz 2 MB SAMS firmware next, as the others have been accounted for.