Info provided by Calvin of Nivlac57 Youtube Channel
Emtech Motorsports offers an adapter plate. The price as of July 8 2025 is US$185 plus shipping. Here is a link for more information: https://www.emtechmotorsports.com/bell-housing-adapter.html See below for required fasteners/dowel pins.
Fasteners required:
Qty 5 Fastenal Part No. (SKU):2139979 pk of 2 , adapter plate to block (M10-1.5 x 30mm 10.9 Black Oxide Alloy Steel Flat Head Socket Cap Screw)
Qty 6 3/8 NC x 1.25 or 1.5" grade 5 or grade 8 bolts - transmission to adapter plate - local hardware store
Qty 3 Fastenal Part No. (SKU):11116162 m10x1.5x 25mm flange head bolt grd 10.9 t/c to flexplate << the size may change if your using an aftermarket torque converter.
Qty 1 pair Dowel pins extra long hollow Allstar Performance Extra-Long Bellhousing Dowel Pins ALL38152 - summit racing
For the more do-it-youself inclined, there is the option of machining your own adapter plare. Frankly for as cheap as the Emtech adapter is, I am not sure why you would, but here are the plans to do it yourself. The Dowel pins are in the same spot in relation to crankshaft center point, so making an adapter to other Chevrolet Transmissions is fairly easy.
You could also use transfer punches if you have access to a 4200 bellhousing and a SBC bellhousing.
We also developed another bellhousing adapter that utilized the factory 4L60e bellhousing. See below:
To avoid having to modify your bellhousing to install your starter, you can use a Tilton Style starter and an adapter that we sell here