See Dan your getting drawn into this build a stroker thing..
What you want one for? You said you dont want anymore than 400, and thats all the Legacy will probably support without spending Thousands.
Plenty of Newage STis in UK running up to 450 on standard STI engine, id say 70% of Newage cars over there now are all on 400 as its just a matter of adding a turbo to them and map.
RCM does New Scooby motors, think they are 1850 EX VAT Sterling, Rcm are that bit more expensive with everything so you could walk into Carol and roche etc etc or any Subaru Dealer and give an 02 Bug or Blob Chassis number and get a price on new short motor..
This stuff isnt rocket science, if you arent going to be going for big hp, then why go and spend extra.
If you were to go for a build motor, i have to capitilise this... FOR FOOK SAKE dont be going and handing over money to un known Ebay sellers, you need to pay a premium and get someone good to do it..
You are talking what 1500gbp odd for the components alone... you need a block... you can buy a block like you have and pay someone to build it for you... how much will that cost? You can buy a CDB, again you buy the CDB and get it converted, its probably going to stand you up around 800 euro... then buy your Lateral kit for 1500 gbp which is roughly 1800 euro. Then get someone to build it all for you, so to me that looks like 2500 euro sitting in boxes ready to be built..
Why spend that when you dont need it or wont use it?????
Heres another thing i would seriously be looking into.... It will need a bit of research, but whats the chances of a FULL Sti long engine Working in your car??????, if it would plug in and run you would be elected, essentially change your setup to an STI iMPREZA, Block, heads, inlet, Everything.. Lift complete thing out of an STI and drop into yours Provided your loom will plug into the STI engine and run it, it can be done. Newage engines are a different thing to Classics, and it would be less of a chance with them 2nd hand.
If that would work, you could be looking at a 2K back on the road with an STI Legacy bill