Is is possible to change / modify the custom ROM you're about to install on your rooted Galaxy S2 (9100)?

Usually, I would install CyanogenMod 10 Nightly build. Then, I'd install GAPPS (google apps). Lastly, I'd restart and it would work.

Now, what I want to do is to replace a default CM (CyanogenMod) apps (SMS, Contact manager/Call manager) with those included in JB 4.1.2 (leaked version).

Is there any way to achieve it?

Thanks in advance for any info and suggestions.