A full write-up isn't all that necessary. Since the beams was an option for the mr2, it's about the same proposition as installing a replacement 5sfe.
The most important thing is knowing which items to reuse from your 5sfe and what you need to buy.
Here's the major items to reuse:
-all motor mounts
-alternator and bracket
-crank pulley
-inlet and outlet hoses
-transmission (or at least the selector shaft, and other tranny hardware if a beams tranny is being converted)
-axles
Here's what you'll want to buy:
-gen3+ water outlet housing
-gen3+ bpipe
-aftermarket camry v6 intake (if you didn't get a maf pipe)
-If converting an AT beams engine, a 3sg(t)e flywheel and clutch set (the 5s flywheel doesn't fit)
-If using an MT beams engine, an uprated 5sfe clutch will work. The stock 5sfe clutch feels barely adequate.
Another good thing to do is to remove a section of the engine lid support brace. If you leave the brace in there, it will make it impossible to do a timing belt later.
Here's a place on ebay.co.uk that has a listing for a gen3+ bpipe at a good price:
TOYOTA MR2 2.0i 16v CAT FRONT PIPE on eBay, also, Toyota, Car Parts, Cars, Parts Vehicles (end time 11-Mar-09 03:10:51 GMT)
Haven't asked if they ship international, but if they do, this should be a much better option than trying to get an exhaust shop to make somthing up.