Ok here goes:
Trailer fender(heavy gauge steel)Northern tool pt#1264(I think) will double check.7"wide coveres the 150 good.
Rear tire probably 160.I had a 150 with the belt,but it was getting a little wide for the rim.
Spring seat,3" springs Drag specialties pt#DS902011 2 reqd.
If you get a mount kit The one part bolts right to the original tank/seat mount bolts.pt#DS902014 it's called a universal front seat bracket.
The bracket that bolts to that,the one the seat actually bolts to is pt#DS902013 universal seat bracketwith square end for HD models.
I had to make the bracket to mount the springs to the frame,but it bolts to the spot the fender bolts go through the frame.
I'll get some pics tomorrow just picked up another '87...going bobber

Metzeler's full line PDF lists "measured rim" and "rims permitted"  In 15" ME880 they list as permitted rims:

140/80-15:  2.75-3.75
140/90-15:  2.75-3.75
150/90-15:  3.00-4.25

Our stock rear wheel has a 2.75" rim.  To be within manufacturer's specs if you want a wider tire than a 140/90 you should lace a wider rim onto your hub.

As for the springer seat.  For my rear mount I have a length of 1" x 1/8" bar stock with a bend/twist on the ends to stretch flat between the stock rear seat mounts....

   
The front mount I'm planning on a bar across the bottom, weld on two four inch risers and a spacer at the top.  This will place the saddle considerably higher and further back than the stock seating position.  Will have to see how it fit me (5'9" 31" inseam) and how it fits Wendy (wife, 6'2" 36" inseam).

May roll the rear mount 90 degrees forward to move rear mount about 1.5" forward/down, and shorten the front mount 1.5" to match.

There is no wrong way to mount a springer saddle.

You know what they say,it's not the size.....

I did,but I've been trying for a month to buy this Savage on craigslist.The guy finally called me today.So I had to buy it.
When I start on this I'm seriously thinking putting in in the tech section.step by step.

Fender is around 27 bucks.
Seat 40.
springs 7 bucks ea.
mounting brackets 2 pcs 25 bucks
about 100 + or - with tax.
I did buy a silver 'Flake seat for the purple one 125 bucks,but it didn't go on it.

My saddle is an Ultima High Noon 13" wide black leather, $49.95 from Jireh Cycles (get the free paper catalog, easier to use than their website)  They have a 5" wide metal flat rear fender for $35.  Don't know if it'll fit, but it's metal and cheap.  They have several pages of various fenders.

Demin, if you can confirm exactly which fender you have that would be cool because I'll order one ASAP. Part 1264 says its dimensions are  28 1/2 x 9 inch wide ?