TWM and iTG both make good filtration systems that could be fitted (a search of either on Google will yield results).
ECUs are many and varied, I too like Motec, pricey, but versatile in my opinion.
Other good alternatives are available too, from almost DIY systems such as megasquirt to major players such as Acell, Electromotive, DFi, MSD to name but a few.
Is the currently installed motor injected?
If not, then also consider the high pressure fuel requirements, pumps/returns, swirlpot(s), pressure regulator, additional sensors for Water Temp, air temp, throttle position, Manifold pressure (or MAF to airboxes) + a crank trigger and if running sequential, a cam position signal too. Consider also the ignition requirements, to keep a distributor, or to switch to a multi-coil setup (coil per plug or wasted spark). The list goes on and depending on your own experience/willingness to 'dive in', careful consideration should also be given to the availability of experienced assistance for setup/tune/problem diagnosis.
Hope I haven't muddied the waters too much - there's a lot to consider but a well injected engine is a great experience indeed!
Just ask anyone who has driven one...
