I think it depends on how long you want to keep the car, like GX said, your's is worth roughly 7g, conversion roughly 7g but with a good low K motor & box so you are looking at 14ish thousand, if you were to spend the same money on a 2nd hand WRX you'll probably be looking at some pretty high repair bills fairly soon, Give the guys at JWS a call, they can supply & fit all the bits, if you buy a complete half cut you'll also have quite a lot of stuff that is left over which you can sell & will offset the cost of the conversion probably bringing it down to 5g.

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Beaten up old 98 Gen 2 Liberty, 13.0, stock V3 STI running gear.
07 Transit motor home
69 VF & 70 VG Valiants needing full restoration
Yamaha Zooma 50cc rocket hopefully going with the Transit.