Tony
The 70-72 freshair base application shouldn't be confusing as only two were used.
But as I am sure you know, the 70-71 parts book has errors claiming 3512765 is freshair base for BJRW when in fact it is 70 E body 340 shaker only.
They only list one base number, 3418709 for freshair 440 B-body 1971, no mention of a 383 number unless there is a 70-71 book that gives it, or I am missing it.
I had both in NOS at one time but I cant recall the taller base part number.
My 72 book shows no air cleaner listings in 14-29-9 so thats no help.
I'll be the first to admit that I am not familiar with all the carb applications alluded to in the parts books used on 70-72 B-BODY and whether or not the different ones actually were used in production but I know you are an expert in that field as you been involved with many.
I was mainly basing my above statement on height, from this partial Fram print that I dug up.
This was the info supplied to Fram that they deigned the shorter base around.
Note the part number 3577491 will not appear in any parts book as this was an assembly... base, lid and filter shipped to the car assembly plant.