FWIW, several 'mild' engines we've had in cars that we took to a bunch of T&T sessions always seemed to like spacers. I had just a magnum 383 in my Coronet at one point and I had 2" of spacer on top of a torker intake and that was faster and if I had had any more spacers and longer bolts I still think it wanted more. It's cheap to experiment with. I whittled 1.25 seconds off the ET on that combo doing little stuff like that - biggest thing I did to it was put the torker on vs the OEM HP intake.
It shocked me just how much difference there is b/t a stock style intake and a decent aftermarket one on even a mild motor. Years ago I was trying to sort out some fitment issues and swapped an Edelbrock Performer RPM intake for a MP M1 dual plane (an aluminum version of the factory HP intake). That motor was neutered after that swap! Completely done before 5k rpm. It was just a flattop 440 w/ 906s and a 509 cam. Sorry...I know this doesn't help the OP. Just made me think of it when I read the previous post.
