Since you don't have complete maintenance records for your SVX you might wish to try a SEARCH on "Auto-Rx". I've used it in all my vehicles and it does what it is advertized to do IMHO. May retard or even stop some of your leaks... If you are lucky!
My engine runs just great on $0.59 per quart Chevron Supreme 10W-30 and regular 3K OCI's.
Oil leaks from seals and gaskets are, unfortunately, at this kind of age & mileage both common & not that inexpensive to cure. When you get around to doing your timing belt I would strongly advise having all the front seals (cams, crank, oil pump, etc.) and the water pump & hoses replaced: you have to take off all the front covers anyway, so don't pay for it twice.
Good luck with your tranny swap.
Cheers!
p.s. You need to join the NorthWest SVX Club if you have not already done so. A truly GREAT group!
