If you do part it out... :confused:, I'd be interested in all the IBM side of things! Is the CPU on the BB socketed so that it can be upgraded to a 486? 
The 386 on the BB are sx and soldered, but a couple companies made a 486 slc upgrade that can be mounted on the 386sx and "take over". The 387 is socketed.
The 486 slc is not like a full 486DX however.
If I remember the 486 slc is basically a 386sx with 486 instruction set and not the other architectural optimizations . The 486 slc do come in clocks at high as 100mhz. If my memory serves I think a company made a revto486 which was a x2 50 mhz slc and evergreen made one that was x3 75 mhz of the bus. Both were compatible with the 2386sx. I have the evergreen 75 mhz 486slc on my 2386sx.
Either way the the bus was still only 25mhz and the math co-processor on the BB "if it has one" is still only 25 mhz. The integer performance is great out of these things, but don't expect overall system performance to dramatically increase.
It is kind of like putting a 68030 on an amiga 500 with out any 32bit ram.
