Neither.
You need more cam for the 4'' arm, more stroke eats up duration and will lower the advertised power range of the cams ur looking at, the motor will run out of steam way before you think.
I look for around 248-254*@ .050 with a mild 408/4'' arm sb
run this one for the hughes
http://www.hughesengines.com/Index/...&level2=RmxhdCBUYXBwZXQsIFNvbGlk&partid=21801
or this one from comp
http://www.compcams.com/Company/CC/cam-specs/Details.aspx?csid=671&sb=2
yes, the rockers will survive.
