ROG tube Reamer op amp changes and mods

[Toney]

Read all I could search for on the reamer and am assembling my parts.
The ROG schem calls for any 741 type single op amp but Torchys veroboard layout  and others have set up for 4558 dual.
Why?
Did this become the way to go due to many wanting to experiment with 4558 type chips.
Now I show my ignorance and sorry if this is a dumb question, but.....
are they interchangable in this circuit or has it been adapted?
Tried to follow Data sheets , reached outer limits of knowledge.
Also....
Will the NULL offset control mod (Torchy's modded Reamer layout) only work with specific chips? Cannot get my hands on an LF351 easily.
And.....
With NE5332(P,AP) and NE 5334(AN,AP,P) chips what ARE those codes refering to ?

[Torchy]

crp

[Toney]

Thanks Torchy,
My gosh, learned some really useful stuff in the last 24 hrs...
Its amazing how quickly the brain flips from frustration to contentment once a previosly mysterious concept is understood.