well the blockhead will need to be milled in order to even fit the duckslide kit. The kit is made to fit the CCI bodies very well. If you are able to mill the body down to CCI specs, then it should fit. I would also look at the "roundhead" bodies (just the already rounded version of the blockhead). It might serve you better.
The barrels will have to have smaller than a 7/8 inch barrel OD. thats what the CCI barrels are, and thats what the kit is fitted to.