Randy, Echoing HRLs thoughts on the pushrod lengths... The '68 Master Parts Catalog lists the pushrod (PN 3836260) length as 11-5/16" for all six cylinder engines (235 and 261), '56-'63. It also lists the rocker adjusting screw as 7/16-20 x 1-9/32". You may wish to check your parts against those dimensions.

Hope that helps.

Doug

1947 2nd-Series GMC FC152 3/4-ton
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1953 Chevy Bel Air Sport Coupe Powerglide