Block question 200 cubic inch rebuild

[Vin Man]

I haven't finalized my decision on which block I am going to use for my rebuild. I have casting numbers C5xx and a C6xx. Both have 7 mains and both only have the 4 bolts for connecting to the trans/bellhousing.

I'm leaning towards the C5 as it is a virgin block - never been gone through before. The C6 is the one I removed from the car, and I know it runs good, but its already 0.040 over.

Are there any differences between the C5 and C6 blocks that I should be aware of before making the final call? I've assumed they are the same, but assuming can be dangerous....

 

[mceachrw]

In 1966, Ford changed the casting of the block to include two additional upper holes in the block for a larger bellhousing and flywheel. Shown is a C5## block on the left and a C6## block on the right. The C6 and later blocks are known as the 'dual pattern' block. The above bellhousings will bolt to the dual-pattern block, using the flywheel, clutch fork and block plate specific to the bell.

text stolen from here:
http://www.phlegm.us/tech/drivetrain/history.html

follow link to see pictures.

in summary, the c6 block will allow you to use the 9" diaphram style clutch instead of the 3-fingered 8-1/2"

 

[Vin Man]

In 1966, Ford changed the casting of the block to include two additional upper holes in the block for a larger bellhousing and flywheel. Shown is a C5## block on the left and a C6## block on the right. The C6 and later blocks are known as the 'dual pattern' block. The above bellhousings will bolt to the dual-pattern block, using the flywheel, clutch fork and block plate specific to the bell.

text stolen from here:
http://www.phlegm.us/tech/drivetrain/history.html

follow link to see pictures.

in summary, the c6 block will allow you to use the 9" diaphram style clutch instead of the 3-fingered 8-1/2"

Thanks. Since I'm using an automatic tranny (C4), I have nothing to worry about - right?

 

[wallaka]

Right. The four-bolt pattern is the old one. Theoretically, '66 should have a couple additional holes to adapt to the larger bellhousings but...might not. Ford sometimes played fast-and-loose with their parts.