I sent my head to COME racing and bought a cam off them to suit, put extractors and 2.5 exhaust on, new manifold and a holley 465, Havent lost to a commodore since except when my accelerator cable broke. I beaten (on the track) VL's non turbo, VP's a VT wagon, lancers really shouldnt be a problem.
My car is manual tho. It makes a big difference. This is in an XF by the way.
Wouldnt it be easier to put a 302 in your car instead? Maybe even a 302 stroker to 351 if your on your P's. 302 in an XE is p plate legal and fuel economy will be similar if not better than a worked 250. I only get 220kms to a tank of premium now.
All up it cost me around 1500 for head and cam, 600 for extractors and exhaust, 400 for carby, 150 for manifold off ebay,and 600 for fitting and tuning, had to regraph the dizzy and get the carby adjusted. and get the head and cam fitted.
Hope that helps.
If you search around in the trading post and things like that you might find yourself a cheap turbo kit. Thats my next move.