any competent engine builder should be able to do it, its not the hardest job in the word (so i'm told)
could try specialised engines or euro engines or burton power or vulcan

(actually dont try vulcan) or one of those sorta places.
dont see it costing the earth...
i THINK youll need to run it on 97ron unleaded tho (ie optimax, SUL etc) as i dont think you can retard the timing on the 1600i like you can on an XR3i, RST etc. etc. coz of the coilpack... i stand to be corrected tho