...can feel the love.
To Integrate my viewpoint: early 420A or 425A have the rib-rail, ALSO has the thick Main webs and taller caps. Yet the Bellhousing is ugly.
I stick to 428/455 blocks for their neatness. The 10%s' here might find the 400 Block stronger with the big-stroke small maind cranks. The 17%s' here may optimize the block strength with them early 420 & 425A blocks.
Block codes do not interest me (except to sell sell sell). Sold YS WS WT YH YH YC YK YK. Several had Steel Caps. I'm left with 1 block now, it is a 71-YC with Stock 4-bolt caps...NOT so exciting huh.

HIS
------------------------------------------------------------------------