DS31203 Cadillac 429 to BOP / Cadillac Transmission Adapter

Cadillac 429 Engine to BOP/C (’68-up Buick/Olds/Pontiac/Cadillac) Transmission Adapter Kit. 5/16 cold rolled steel, CNC cut bolt holes and threads. Includes countersunk bolts (4) and 1 piece flex plate spacers(3). You will need to provide (4) normal transmission-to-engine bolts, (2) 5/16″ bolts the same length, and (2) longer 5/16″ bolts (optional), which can be purchased at any hardware store. The lengths of these additional bolts will vary depending on the transmission and engine block used, but the bolt head style can be whatever is easy to get.

This fits the ‘standard’ (most common) 429-specific trans bolt pattern found on the back of 429 Cadillac engines. If the BOP/C trans lines up with the dowel pins on the back of your block, and your block has bolt holes for the starter, but none of the 6 transmission bolt holes line up, this is probably the adapter you need. If you block has starter mounting bolt holes, but the dowel pins don’t line up with your BOP/C transmission, look very closely – there is probably a factory transmission adapter bolted to the back of the block, and removing that adapter should reveal the bolt pattern used for this 429 to Chevy trans adapter. There are exceptions, but they are exceedingly rare. If you have a factory transmission adapter that has dowel pins that line up with the BOP/C pattern, but the block does not, and you do not have starter mounting bolt holes on the block, then there is a good chance this adapter will work in conjunction with the factory adapter, but will require different ring gear spacing (either the rare factory flex plate for use with the factory adapter, or an aftermarket flex plate or flywheel – and you will need to specify the alternate ring gear spacing when ordering those items). If you have an early block without the starter mounting bolt holes, the kDS31301 adapter will adapt a Chevy pattern transmission, without stacking a factory adapter in there (there is no BOP/C adapter for the early blocks).

Note: If you are using  light duty transmission (Powerglide, TH350, TH700R4, TH200R4, 4L60, 4L60E, or 4L65E), or certain aftermarket performance converters for the bigger transmissions, you will need a torque converter adapter DS31111, as the light duty transmissions have a different converter bolt pattern.