318 build with XE268 AND 302 heads

BTW, your static CR will be no better than 8.6 IF you have 318 flat top pistons, AND you use the Mr gasket 1121G head gaskets . If you have the 318 pistons with 4 valve reliefs and standard Felpro head gaskets, then your SCR will be 7.5:1.... I ain't fooling you. So that is why going with too much cam will suck.... the late closing intake of the longer duration cam will KILL the compression and it will indeed be a dog in the low RPM ranges. A rumbly idle will come at a very high cost to low end torque with your engine.

What were your cranking compression numbers? Is this a Magnum 318 perchance? (Not if you are looking at the rocker set that you linked.) If you have the heads off now, see if the pistons are flat top or have 4 valve 'eyebrows'.

Honestly, I would be looking a 256 to 252 duration cam from the Voodoo series for this thing and wanted good low end torque. I have run that kinda of cam before and it is where you want to be for torque and a stock torque converter. The 268 duration level cams are a compromise cam but you need some real CR to work with it well down in the low RPM's. Guys use it because they may drag race and they are spinning up the engines anyway and putting in a higher stall speed torque converter does not hurt that situation.

If you can let us know about the pistons and the present cranking compression, then better advice can be given. But all the advice so far is honestly on target for what you want to do with your engine.