I am running the Unilite non vacuum advance with Accel spark box.  Playing with the initial advance I don't hear any detonation running the engine to 4K sitting in the garage no matter how much is dialed in.  Does get to the point that there is not a miss as such but running rough if it goes too far.  After many years of operating noisy machinery my hearing is challenged to say the least and I may not hear spark knock over the exhaust and other engine noises.  Right now it is set at 16* initial and 38* total but still seems a little rough.  I want the full potential of the engine without doing any damage.  This is a street warrior only so test and tune at a track won't happen.  If anyone has close to the same combination (side oiler, aluminum heads & 2 X 4 intake) in a Mustang and figured out the ideal settings I would appreciate the figures.

Also try to lift the gas pedal from underneath with your foot.  If it returns to set idle something is in a bind from pedal to carb.  Another test would be to quickly stab at the pedal and release seeing if it returns to your setting.  Good luck.

My guess on the blocks would be cost.  I heard that the 427 blocks after casting were fed down a long cooling tunnel to minimize stress.  Others might chime in on this.  Remember time = money.

Watching the Robert Pond interview he stated that he normally shifted at 9000+.  That is the stratosphere for the most of us.  It would be nice to know what the bottom end of our FE's might handle - just the rotating assembly.  There are too many valvetrain possibilities out there so let's just figure crank, rods and pistons.  Say stock 390, 427 and 428.  Then add in some common stroker combinations.  Mine is a 427 side oiler block 4.250 bore and 4.125 stroke with 6.700 H beam rods.
If we can get a ballpark figure for the bottom end then there would be no need to spend extra money on the valvetrain to go beyond the limitations of the rest of the engine.

Welding will "draw" metal and the others chiming in are right.  Be careful of your heat setting on the welder so you don't burn through.  After laying two beads opposite each other, you may be able to use a punch from the bottom on the welds to coax it out of the bore.

Had this happen years ago myself.  Went to the hardware store and bought (4) 7/16-14 bolts about 4" long.  Screwed them in the bell holes with about 1" of threads exposed.  This ensures that the tranny is close to where it needs to go to slip in.  It will also show how much gap there is between the tranny and bell on all four corners and is holding the weight.  Grab the tailshaft and wiggle while pushing forward and it should slip right on in.  Another time I got frustrated and called it a day.  Next morning crawled under the car, grabbed the tailshaft and it slid right in - go figure.  A two or three beer break would probably work also.

Pair of Stage 2 Edelbrocks set up for Solid Roller cam.  Originally set up for Hydraulic Roller from Keith Craft Racing.  Correct Comp Cams springs for the solid cam.  Heads will need to be surfaced due to detonation guessing .010 - .015.  Located in Kernersville, NC (North Central between Winston-Salem and Greensboro).  I have close to 4K in the pair.  Asking $2,000 for them plus shipping.  I would prefer that any potential buyer or their representative come in person to inspect them if possible.  I have the capacity to disassemble the springs etc to view inside.  Can be reached at 336-723- Twenty four thirty eight.
 Happy FE New Year.  By the way these are 427 castings.  My apologies to anyone calling about these heads.  Due to the daily number of calls trying to sell me something, I don't answer any calls with an unknown number.. Please leave message with name and number and I will get back to you.