[scooder]

Surly a sleeve over the old spiral adds another leak point/risk.
I'd imagine that whatever is used to hold or support the seal in the timing cover and sump will also add another, and complicate further removal of the timing cover should the need arise?
I'm not anti new ideas, just in the if it ain't broke, or keep it simple camp.
Sure they tend to weep a little often times, but only a weep.
This is my opinion.
Could I ask as to why you feel it's necessary to do this modification? Genuinely interested in your opinion, not start a smit slinging contest.