You'll want to check junkyard listings on car-part.com or skim places like Craigslist or FB marketplace to see what's around. Not sure what rebuild parts are on the market, since it's not a common engine that gets overhauled. I'm sure some manufacturers make the parts, but if you're just looking to get up and running, a used engine will probably do it for a fraction of the cost.
Good luck, I know Series 1's aren't the most discussed or tinkered with, aside from a rare few who went that route.
The series 1 engines don't garner much popularity as the power rating is quite a bit less than what the 95-07 series II and Series III engines offer. IMO, finding a low mileage series 1 engine in the junkyards will be hard to find but you could start with a high miles engine and rebuild. The decision you will be faced with is cost. Is it better to stay with the series 1 and rebuild or swap in a series II or III engine that you might also have to rebuild? Easiest solution, just buy a rebuilt series 1 shortblock and install that.
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