I've been told and used the theory that spreading the LSA gives up bottom end power and increases the top end power, a tighter LSA will affect the manifold vacuum and idle quality and sounds shruggy
I have pump gas stroker like yours on the engine stand that has a solid roller Crower that has 261@.050 on the intake lobes with .430 lobe lift and 263@.050 with the same lobe lift and it is ground on a 105 LSA, it has a set of ported 440-1 with a set of Harlnad Sharp 1.55 ratio rockers. I have ran it on a engine run stand and it idles very nicely shruggy
I like bottom end power more than revving the heck(above 6000 RPM out of the motor to make power work
On your deal with the stick shift and 3.91 gears I would go with the 108 LSA and install it between 103 to 105 intake lobe center and plan on shifting it between 5500 RPM and 6300 RPM, where ever it quits pulling hard scope

Last edited by Cab_Burge; 03/21/19 11:56 AM.
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)