engine alignment probs
"Gen 3 Hemi Crate Engines (5.7L, 6.1L, 6.4L) /67-76 A-body / 66-74 B-body / 70-74 E-body applications: From the center of the crankshaft to the top of the K-frame, the correct distance is 5-5/8 for A-bodies (5-7/8 with spool mounts) and 5-3/8 for B&E-bodies (6 with spool mounts). The engine is also offset towards the passenger-side. Measure from the center of the crankshaft to each frame rail, the difference should be 3-1/4 for A-bodies (2-3/8 with spool mounts) and 2-1/2 for B&E-bodies."
So, based on your set up (6.1 with biscuit mounts) your measurements are: From the center of the crankshaft to the top of the K-frame, the correct distance is 5-5/8. Engine is also offset towards the passenger-side. Measure from the center of the crankshaft to each frame rail, the difference should be 3-1/4. Tailshaft is 2 - 2.5 degrees down from front of engine. And yes, the engine must be in a strait line from front to back.
I got info from this link: http://www.ttiexhaust.com/Footnotes/Footnotes.htm