I've used plastiguage but am curious as to how to use bearing scrapers and time saver compound. I want to put my engine together with everything fitting correctly. Also, even if babbitt looks good, should it be rebabbitted? I suppose metal fatigue would make the babbitt weaker and cause it to pound out quickly? Or am I wrong?

I have used time saver and it beats scraping MHO
As far as the babbitt if it looks solid and is not out of round [piled to one side of split] Id use it.
Jake C.

How many shims were under the mains? That's a hint to the condition of the babbitt. If you don't know the history of the engine and you have it down that far, it's better to have it poured and line bored to match your crank. Few experienced mechanics can scrape a bearing and none as accurate as a line boring. Have you checked the crank mains and throws for roundness? Is the crank straight?

The Ford service manual shows the procedure for scraping the bearings. It's not a difficult procedure; just time consuming. You'll need Prussian Blue to find where the high spots are to be scraped off. I aim for at least 75-80% bearing contact and set for a little on the tight side. That way the bearing clearance will 'self adjust' to suit after a few hours of running. I have done all the bearings, including the three for the crankshaft, this way with good results.
I haven't used Timesaver so can't help there, but understand it gives a more accurate bearing clearance. I believe it is some kind of abrasive compound.
Old babbitt is the way to go if it's in good condition. All mine is original and shows no sign of deterioration yet. There are stories of modern babbitt failing.

We use it on every engine, like it so much we made up kits that have all four grades. Just enough to do a couple T's. We keep it stock for our "do it yourself" customers. We also have timesaver kits for hard metals (valves, timing gears, ring/pinion gears, etc.) too.

Here's two links to it on our website:

Product:
http://modeltengine.com/products.htm (1/3 down the page)

Instructions:
http://modeltengine.com/InfoPage.htm#Timesaver%20Instructions

IMHO timesaver is OK to refit used bearings. If the machining job is done properly on a new machining job there is no need for it. It is not difficult at all to machine for a .001" fit! I have used it and will again for a FIX job. If I make a mistake on a new job I will redo it.

Time Saver will give you a 100% bearing without scraping. Great Stuff!