Re: 4litre to 5 litre conversion
No point tellin him to buy a 5l - he wont have a bar of it lol He's dead set on doing it.
Of some of the things you mentioned...
K Frame? Probably yes although fordfan351 has modified his to suit the V8. But looking at my K frame they seem totally different to the 6. For starters they dont have that bar which stoops you getting the sump off.
front suspension? 8's had uprated springs and uprated swaybars.
radiator? Yes they had an uprated radiator.
You'll need fuel lines as the fuel filter is under the rear seat as apposed to being on the firewall on 6's. Brake booster was uprated, you'll need the tacho dash from an 8cyl, exhaust obviously, they also had alloy tailshafts. Theres probably a lot missed which you'll find when you get to doing it.
If you need, I can get a set of engine bay wiring looms from an eb2 xr8 for $150 (neg)
Dot Aye You