Hi I also did the same conversion as you, mine were from an Escort, which used the same thread allowing me to use the original bolts , I also used the original pipe and hose with no modification apart from bending the pipe a tad to accommodate the bigger caliper.
Just a note on using the original disc, they are a tad small and the pad will hang over the edge and you will also note the disc dose not run central in the caliper, you will need to put in a spacer to centralise it.
I bought a set of Lotus sunbeam disc (from speedy spares UK)as this disc and p16 caliper is the original set up on that model, they are bigger in diameter so all of the pad will contact the surface and also thicker, and they come with the correct offset for the caliper ,everything bolted up using the original bolts.
These calipers are more than adequate for the weight of the Avenger, they are still the favourite caliper for many a Escort race car