$150.... that's a great price... worse case is you part it out and get your money back... or more.....

The brake light looks like the one on my trailer.....

There are several tanks and speedo's on EBay.    
Do a search for: "Suzuki (LS650, LS 650, S40, Savage)".  

Everything inside the parenthsis are "OR's".  So the results are anything that has "Suzuki LS650" or "Suzuki LS 650 " or "Suzuki S40" or "Suzuki Savage".

Remember to include the "stores" items.  Several Sellers make their money but tearing apart bikes.

As for speed of the LS650,  depends on how you mod it.   The bike is different than most anything else out there.   It's speed is also just different.   Torquey enough to surpirse most other bikers .... long enough to keep the front wheel down. ..... but don't look for white knuckles at top-end.   It's a 650 but it's only one cylinder.......

  It's not a sport bike or a cruiser so don't even try to compare it to them......  unless it's comparing it to the others on ease of maintenance....  where it would probably win.   Looking at the pict's of your garage,  it may turn out to be the bike you use to run over to the parts dealer to get whatever you need to keep the other bikes running.

It's old school design, with low oil pressure.  Remember to change the oil regularly, and don't go cheap on the oil.