Looking at the heads there are a mix of bolts.  Some grade 7 with six tick marks, some with four tick marks (?), some grade 5 with three tick marks and all have an F in the center.  Four bolts just have FT in the center.

I have not removed them to measure the lengths yet.  But I thought it odd on one head the three center bolts have a grade 7 then a grade 5 then one with four tick marks.  The bottom five bolts under the exhaust header are a mix with six and four tick marks

1959 Edsel Ranger, 1916 Ford "speedster"
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