Yeah I did as Thom did and used tek screws.  Nut sert or riv nuts would be preferable if you can get access to them

It's not the "correct way" to do it but I've fitted one with self tappers before, if you wanted to do it a bit better than that I've used nutserts and then bolted it in

@deankxf @Thom has anyone put an an xg pedal in an xf.   I got my hands on an xg pedal and an AU v8 cable. Pretty sure the cable will just click in.   I thought the XG pedal would bolt straight in as XF and XG are very similar. But the mounting bolts in the firewall are slightly off. Has anyone done this before and what’s the best way to achieve this?

This may be of use. https://www.gumtree.com.au/s-ad/bundaberg-central/brakes-suspension/ford-power-steering-box/1325331564

In my mind, the trouble (and risk) is all crossflows are likely worn out these days. They're 20yrs older, with 250-300,000km +.   IMO, any replacement sec/hand engine, could have a worn cam also? Use of modern Synthetic/Non-Zinc engine oils in flat-tappet engines (aka crossflows) are probably not helping.   Yes, could definitely use a Micrometer to measure cam lift, and compare with the factory specs. Moot point though, as if the pushrods are straight, then either cam and/or lifters are toast.   Crossflow 6cyl's (and flat-tappet Clevo's/Windsor's too), need 15w/40 or 20w/50 mineral oil IMO. Easiest way I found, is to use diesel grade mineral oils, and double check the zinc content from manufacturer specs.

I used a T-handle lifter removal tool for my lifters.   Initially to get them out, I applied a hammer type force downwards using my palm on the tool handle, whilst at the same time, applying upwards tension on the handle with my other hand.   I later learned that the trick is to rotate the lifters, as you try to lift them in or out. (they're an incredibly precise fit)

most come straight up, some need poking along a bit to the bigger opening.
you are only going to need to check a couple, if one's stuffed, its' game over for that cam, then in my opinion i'd fit another engine (crossflow) to just be done with it sooner.    doing an engine conversion i like to have everything  ready to go, i don't like pulling a running car apart for long, otherwise it snowballs into an unfinished project easy.    fitting a cam with the engine in the car sounds like a nightmare to me, but it can be done.    i'd sooner pull the engine out. (engine out in an XF with the trans still on it is easy, can be done in a few hours if you are set up for it. i used to start undoing stuff friday night, wake up pull the engine out before lunch, and bolt the replacement engine up to the gearbox etc and complete it as much as possible *changing welsh plug behind flywheel and having new hoses, belts, oils etc ready to go. then after lunch drop the engine in the bay and do up all the under side of the car first .. exhaust, tailshaft, gearbox, engine mounts etc.. then sunday i'd just do all the easy stuff and test drive it before it went back to work on Monday good for another 50,000km of zero maintenance other than oil changes.      basically a piece of coathanger would be good enough. sit a pushrod in and get a measurement of how high it comes up and down..  do it same for others, if a cam or lifter is wiped it's going to be 1mm difference pretty confidently. could likely hold a ruler up to the side and see how much the pushrod travels even for 1mm ish  change

If I got a micrometer how would I check the lift on the cam? 

Ok I'll give it a go. Also how do you get it out past the head

they won't be mushroomed, it will be carbon build up on them. 
just work them up and down as much force upwards as you can each time, they'll come out.  if you can rotate the engine a little to put that lifter at the lowest position first, it will get sort of a run up in a yank to pull it out, i don't think you'll get much spray down the side of it, it will just need working up and down.