Alright Shah
It is the way forward :) I always liked the idea of keeping the same engine in the car so it was original, hence turboing the NA. I was tempted with the SRT too, the issues were thought that above the cost of buying and importing it there is installation, there is also the probabilty of fabrication needed for the downpipe as their steering rack is the other side. There are quite a few parts that are oversized for the actually requirement of the conversion like size of injectors, turbo (which isn't named only a spec'd one etc. It is realistic that that it would be quite laggy fine if your running the strips but not for everyday use.
I would be wary of the advertised engine as I looked at one from that company before and they were saying it had been uprated internally etc because of this part attached which was all wrong as it was only a japanese gimmick, saying it balances the camshafts!! The kit supplied by SPC would be Garrett turbo, AEM management and other branded parts and all new, of course it depends on budget so if you get good prices for the other parts it would be cheaper.
It would be best to uprate the injectors and fuel pump to get the best efficiency from the engine otherwise it'll starve and you won't get most power and smooth running.
I don't think the sprag clutch is a necessity but i would definately install a transmission cooler to assist the internals of the transmission and if needs be at a later date look at a valve body upgrade, which replaces the inners of the transmission that take the fluid to each gear making greater pressure thus increasing the speed of gear changing and less pressure on the clutch!
I'll PM you list and estimated costings.
Cheers