need some advice on gq

[NOP054]

hey all, i am having a real bad trot at the moment with my gq its a 96 wagon ti auto 4.2 efi. About a month ago i finished fitting a reco "extreme" auto from the wholesale automatics guys from down south. i haven't even done 2000 k's since i fitted it and now i think ive done a head gasket. I did a trip to the coast on christmas day, before i left i checked my fluids ect all was good. On my way back i got around 2k's from my house and i noticed my car was getting hot around 3/4 on the temp gauge. When i pulled up at home i found that all the coolant had been dumped into the sump, from my expiriences my initial thought is head gasket or cracked head. is there any other explanation for this, do the tb42's have welsh plugs in the head? a water pump backing plate that is prone to crack? any info would be great.

i am weighing up my options with a few different ideas and if anyone could give me a rough estimate on how much i would be looking at it would be great.

im looking for most cost efective way to boost power and i want some decent fuel consumption around 8k's to litre would be good

1. injected holden v8 conversion using my gearbox probably 5.7

2.vh45 using my box

2. 6.2 or 6.5 ltr chev deisel conversion using my box

3. rebuilding and turboeing the petrol and putting it on gas

any other ideas?

[BOOSTED GQ]

more than likley the head get it checked the. the timing cover in behind the water pump can eat out due to electrolicis but if its had good coolant most of its life in unlikley, thay were prone to head and head gasket dramas.
as for the engine the tb can be built tough and good power I like the holden V8 or gen3 so on I dont like the chev diesels, like the vh45 but I think it would get pricy.