Skooter,

Sounds like in the end you need to replace the current COE engine "updraft" style intake and corresponding exhaust with a "downdraft" intake and exhaust manifold set like Mike B suggested above to provide best fit when installing the 261 into your 3100.

Looking forward to seeing pictures of your 261 acquisition. thumbs_up


~ Dan
1951 Chevy 3 window 3100
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"My Grandpa Carl's Truck and How it Became Mine"
1966 Chevelle (Wife's Hot Rod) | 2013 Chevy Silverado (Current daily driver)
US Army MSG Retired (1977-1998) | Com Fac Maint Lead Tech Retired (1998-2021)