Low Vacuum Issue/Big cam

68, back in around 1980 we used that cam in our stock 340s. It ruined everything about them. On top of screwing up vacuum and idle and driveablty at lower engine speeds, it slowed them down as we refused to gear them lower and shift them higher than 5800.
Hate to say it but I'd yank that cam out and use a stock 340 cam or a new generation cam from a reputable source, MOPAR has some I think now that work well. That cam is too big for any sort of low end even with a high compression 340 and even a 360. Hate to see how a 318 feels with one. Not saying it is bad, just saying it is not too good for street action or where you want to retain some semblance of driveability, idle, low end torque and not to mention, fuel economy.
My opinion, I am sure others have had better results.