The best way to be sure is to buy the adjustable one and measure. Stock length may work, I was told it would on my application but there is slight play in mine after taking the valve lash out. I should have measured to begin with.
2014 F-150 STX Sport SCab - Stock
1967 Coupe 306 roller block, E303 cam X302 heads, Crane 1.7RR, T5, 8.8 rear 3.73, CSRP Power discs