Right!!! The 1965 LA 273 uses 5/16-18 threaded bolts into the heads & at a slightly different angle, where as the 1966 & up use the 3/8-16 bolts... BUT... if you should find a 65 4bbl intake cheap, And, if you are handy with drilling holes & things like that, it is fairly easy to open up the intake's 5/16 holes for the larger 3/8 bolt size and taking the slight angle change into account... I've done several of these for peeps and never has been a problem!!!