Have a 261 in my '49 GMC half ton. The rear of the valve cover (Offy) is close to the firewall be clears it okay. No rubbing. In fact, I lengthened the cowl drain hose and put it behind the rear of the valve cover so it would dump water away from the cover itself. You may be able to see the clearances on some of the pics in my engine rebuild album. I have the single front mount and the two rear mounts on my 261.

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Country Roads, West (By God) Virginia
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