I have a 1.000 diameter stainless bar and a few homemade pucks the fit in the housing ends. I also always make a 2" long inner sleeve that is machined to the exact I.D of the tubes. I press-in sleeves using bar and pucks, then intall center section and new axle shaft with bearings and tighten bearing retaining plates. it's pretty easy to tell if your lined up then. I tac welding in 4 locations, remove axles/center section, re-intall 1" bar and spacers and completely weld.
don't know about the heads flow numbers, there not the infamous double hump 461's heads, these are 896's that came with small valves (changed to 2.02/1.60) but i like they only have 59cc combution heads before decking, so compession is 10;1 even with stock pistions.
other than clearancing the valves no work was dont, (but this series has heavy casting, no cracking or other problems) nitrous is in the plans down the road, maybe by end of summer