Edelbrock 750 performer

[shaker71]

Question here!  I installed a 750 performer on my 383 and after trying to tune it i seen that i may have the wrong adapter plate on. Quadrajet Adapter Kit #2697 (Do not use an open adapter!) Why can i not run an open adapter?  Here http://static.summitracing.com/global/images/instructions/edl-1407.pdf  Just woundering about number 4

[Moparal]

You can't use that spread bore open adaptor on that 750 because of the gasket seal will not work and you will have a vacuum leak.