Al,
We run the 600-13 heads on our motor in our dragster.
Motor was done by Best Machine about 4 years ago.
At that time we got the latest design 600-13 head that Indy just redesigned.
Motor is all alum Indy spread bore / raised cam block. 622 CI
Have had no problems with heads.
You are welcome to call me.

seven 1 two 2 five 3 four 1 nine 0

Chuck

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