I know 99 was the first year you could get it across the range, but was it also the first year it was available in the higher end magna’s like the Alteria

It was avaliable only in the Verada's from 96 I believe.

Yep, the 3.5L engine (aka 6G74) was standard on the first 3rd gen Verada (KE) then it first became available on the Magna when the TH series came out.

That would be my car :)

Very late 96' they started production on the Veradas.