The 100 amp alternator is larger than the stock 60 amp unit, but it is still close to a bolt on unit.   The output post is rotated from the stock position on the 60 amp alternator of 1:00 to about 5:00 on the 100 amp alternator (times are based on looking at alternator from front of vehicle).

The first thing you need to do for this upgrade is to disconnect the negative side of your battery terminal.  Next, remove the air box and all of the attached vacuum boxes to gain access to the alternator. Disconnect and remove the old 60 amp alternator.  Remove the lower alternator bracket.

You will have to remove all of your fan belts to install a new longer alternator fan belt.  I recommend that you save the old belt and not just cut it off.

The hardest modification is to the lower alternator bracket.  I recommend that you buy a new bracket (Toyota P/N 16381-65010) so you can keep the old alternator, fan belt and bracket as a trail spare.  The lower bracket needs to be modified by welding a 1/4"x1" by 4 inch long piece of steel to it.

(The piece I used is about 4.5 inches long). After cutting your piece of steel, drill a 7/16" hole at one end of the piece of steel. Next, I clamped the pieces together and tack welded the piece of steel to the bracket.  I then cut the corners off of the extension to match the factory bracket.

I installed the 100 amp alternator with the modified lower bracket to make sure everything lined up. Once I determined it was a good fit, I welded the bracket together permanently and added a nice coat of paint.

There are a couple of small modifications that need to be done to the alternator.   The first modification is to the output post.  I removed the existing bottom retaining nut and added a new thicker nut with lock washer.

This mod is necessary to gain clearance for the single output post wire connector that has "fangs" on it.  The output post is 8 x 1.25.  Keep the retaining nut to use to attach the connector.

The location of the hole is shown in the picture below.  It is located between the two rips in the cover as shown.

It is about 3/8" up from the lower rib and 3/8" in from the left edge.  Be careful when drilling this hole.  The aluminum is very thin and doesn't need a lot of force.  If you want to be safe, you can remove the cover to drill the hole.  I widened the hole a little bit with the 1/4" bit.

Another small mod is to the output post cap.  If you get your alternator from a junk yard, try to keep the MR2 cap. The picture shows the original 60 amp alternator cap that was modified by drilling a 1/4" - 5/16" hole in the center of the cap to allow the output post to stick through it.

The cap on the right is the MR2 cap.  It is a soft rubber cap and doesn't stay on to well because it is nearly up side down when installed.  If you use the original cap, try clipping it on the 100 amp alternator before you put alternator in the Truck/4Runner.  It is a very snug fit, but it will fit.

A small modification is needed on the output post connector.  The hole needs to be enlarged.  I held the connector with vice grips and enlarged the hole with a 5/16" drill bit.

The last thing that needs to be done to bring it all together is to purchase a new fan belt.  I recommend a belt that is 2 - 2.5 inches longer than stock.  If you go too much over stock (my first belt was 3.5 inches longer), the alternator will interfere with the vacuum boxes bolted to the air cleaner.

Buying a longer fan belt is not that difficult.  At the auto parts store, I looked up the original fan belt for my truck.  It was a Ribbed V-Belt, number 465K4.  These numbers are the key.

465 is the length of the belt.   I believe it is 46.5 inches long.  The K4 stands for the 4 ribs in the belt.   The belt I bought was 2.5 inches longer than stock.

So add 25 to the 465 to get 490.  Keep the K4  because the number of ribs doesn't change and the new belt I purchased is a Ribbed V-Belt, number 490K4.  Different brands will have different numbering screams, so just ask someone to help you out.

When bolting everything together, I would put the top bolt in first, then mount the modified lower bracket to the block and the alternator.  Leave the bolt that goes into the block loose enough to let the bracket swing up and down during adjustment.

Install the new fan belt and adjust the belt tension.  Tighten the lower adjusting bolt on the alternator.  Then tighten the upper alternator bolt.   Then tighten the lower bracket bolt at the engine block.

Connect the connectors to the alternator and install the modified output post cap.  Once the cap is installed, cover the exposed post with some silicone sealant just to be safe.  Remember that the post will be hot when the battery is reconnected.

Re-install the air cleaner assembly and vacuum boxes and test out your added amps.  This modification even looks factory.

I have been running this modification for over a year now and I have not had any problems with it at all.  It has even worked great while wincing.