Tim, I expect you’ll get lots of input but IMHO…
Read the Miles Wilkins Twincam book (if you don’t have it - get it!). Although he doesn’t discuss 1600 blocks (I sense he doesn’t agree with them) most of the internals are common and he has lots of good info on rods, cranks, machining, etc.
Have you just got a 711M bottom end - or complete with tc head? If bottom end only and you’re using your existing head you’ll need the appropriate spacer for the timing case plus different timing chain and chain tensioner, etc.
I run a 1600 block (not 711M unfortunately) - but the engine was in the car when I bought it. The 2 PO’s did some racing but to date I’m a road user only. I have not touched the bottom end yet but I have had the head rebuilt.
When built up, my block was bored out .50 mm (.020 “) - yields just under 1700 cc as I recall. 1600 blocks accomodate this fine - a good 711M should be OK for 1.0 mm (.040”). You just have to ask yourself why you want to do it, how much you want to bore out and how much money you want to spend.
Don’t know what pistons I have for sure. When the head was off for rebuild they appeared to be standard Hepolites (+.020" of course) - probably from the '80s - and I have an empty Hepolite box that came with the car so it’s a fair probability. There’s a lot on the forum about pistons.
125E rods are fine if you aren’t going to push the rev’s beyond recommendations.
I would recommend uprated bolts, studs, etc. wherever (ARP) - with square caps of course (which would be on a 711M anyway) - it’s a small investment.
Use the standard oil pump. The later screw on filter type is nice (wish I had one). Unless you’re racing, I think the high pressure pump will cause more problems than it’s worth.
You’ll run into some minor issues like you often have to use the traditional exhaust side engine mount on both sides. The normal inlet side mount is higher than the exhaust mount to ensure he carb’s clear the footwell on the standard engine - but on the 1600’s they will almost certainly push your valve cover right up to or over the bonnet line.
Where? - Sorry, can’t help you. I know a very good engine builder but I’m afraid he’s in Sydney (Oz)!
Have fun.