I play through a 68 Fender bassman head into a JCM800 cab. I Use a Marshall Jackhammer for my overdrive. But what I want is to have a dirty clean channel. Pretty much I need to keep a a slighty dirt channel and use the jackhammer to keep more gain. Anyone have any ideas how I could do this.

I was thinking of getting an MXR Micro Amp and keeping the gain low and using the Jackhammer to cut through more.

I have a 67 Bassman head... You need 2 pedals one that will give you some dirt and the other to give you the overdrive. A tube Screamer is a good choice for the dirt but there's tons of other great pedals on the market. Boss SD1 overdrive will do great too... I make my own pedals now and this will give you complete control over the tone your going for!

Or you can add a preamp section to your bassman... Jim Marshall got started with his Marshall amps by modifying a Bassman!

as stated 2xPedals may be your answer.
In the long term you must concider a 2 channel amp.
The Micro amp will push your front end, but your amp will be louder since you have only the one channel. If you've got the snaps, Rivera or VHT have fabulous clean and distorted channels. The DSL sounds nice.
The Wanka