If you want to fit a 150 all you need is the tyre fitted to your wheel and a spacer around 2-3mm thick, or 3/32" - 1/8", to go behind the rear wheel pulley. Simple as that.

If you want to go wider, it makes sense to me to buy a kit with all the parts in one package.

 

Yeah, if you're going any wider than a 150, more has to change. Basically you could piece a kit together, but the nice thing about the kits is that there is no question whether all the parts are right. If you buy the parts yourself, you have to know exactly what parts you need for your bike.

If you want to try and price out the parts, find a kit you like and identify the parts by looking at the picture. Then go to JP and price the individual parts. They are all available, but it's not really worth it. I looked into the same idea for my wife's 98 Softail. Once I started getting into spacing the primary and getting a longer mainshaft, etc...I lost interest in trying to piece a kit together myself.

 

Nah, That's another ploy by the politically correct police to genericize us into oblivion!!! I refuse to comply, I stand by my convictions as a non conformist and will either in my head, or with a calculator if need be multiply every MM by .039370078, or divide it by 25.4 and get the english equivelent!!!!!!

(Actually my OP was supposed to be a good hearted "rib", and I guess a lame attempt at humor, I'll admit it, I'm strange, If I'm trying to be a dick, it'll be obvious that I'm trying, but I can't hide the fact that I am when when I'm not trying!)

 

Good man! Imperialism wins....

The only metric stuff on my old lady are the battery terminal bolts, but my other later bikes have a few metric things sneaked on them. Slowly but surely H-Ds are going that way, probably the rest of US industry.

Here in the UK in the 60s the British bike industry adopted the US threads, so I had to buy AF tools in addition to my Whitworth stuff. I now have metric too....

So excuse my dig in the ribs over US metrication! We've already been round that bouy.

 

If you do this let us know how it works out. Sounds like a quick and easy solution to get a bit wider rear meat.
Pics are always great too.

 

The thing is that I would like to get the stuff individually (looking for good deals like a used wheel, fender or whatever..) so in time I have all that I need and it's better for the wallet jeje.