Welcome!
It's not that bad. Best thing you could do first is get an 94-96 cross member which will be set up for duals. Not sure if the L99 (4.3L aka most civi sedans) used the 'double' but 9C1s, wagons, and SS all did). Has that 2nd 'dent' for the exhaust. Other than that shouldn't be too hard.
Pretty sure Fred K has done it with his 454 swap, and others.