Bosch BIP373 Ignition Driver

VB921's are going out of service, and becoming harder to find, even for bulk purchases. The best replacement for it is the Bosch BIP373, which comes in the same TO220 package and has the same pin-out as the VB921. It has a few features that actually make it better than the VB921:

It limits the current at 11.5 Amps, rather than the 7.5 Amps of the VB921. This allows for more coil current (at the risk of heating the coil too much - many coils will not support 11.5 Amps on a sustained basis, so you will still want to set your dwell appropriately).
Unlike the VB921, the BIP373 has temperature shut-off circuitry (Bosch calls it a 'soft thermal shutdown'). If you have your dwell settings too high, or even inverted, and you overheat the BIP373, it will reach a temperature threshold of 195°C (383°F), and shut the coil current off entirely (no spark) until the BIP373 cools below the temp threshold.

The Bosch BIP373 ignition module is nearly a drop in replacement for the VB921, with one exception: you must use a mica insulator kit between the BIP373 and heat sink when you mount it because the mounting tab is 'live'.

This part is fairly rare (at the time this is written) and cannot be sourced from Digi-Key, etc., so people wanting them will need to get them from DIYautotune.

The datasheet is here:

bip373_datasheet.pdf

MegaSquirt^® and MicroSquirt^® controllers are experimental devices intended for educational purposes.
MegaSquirt^® and MicroSquirt^® controllers are not for sale or use on pollution controlled vehicles. Check the laws that apply in your locality to determine if using a MegaSquirt^® or MicroSquirt^® controller is legal for your application.