Here are just some thoughts.

1] Wooden side rebates are cool in a gizomtic way.
But as a usable tool I would definitely avoid them.

(Of course, as with all advice on the Porch, YMMV and I'm sure
many folks have different thoughts.)

2] The dream team, of course, is a pair of the Stanley (or LieNielsen)
side rebates.  But be prepared to pay a fortune
(OTOH, Father's day _is coming up).

3] An excellent fall back to the 98/99 pair (see item #2, Jeff)
is to get find yourself a nice *pair* of Stanley #79s.

Some folks don't like the "trailing blade" on the 79 [but it's never
bothered me]  But in any case have two solves this problem.  And,
if you're not in a rush you should be able to find two 79 for the price
of _either_ a 98 _or_ a 99 by itself.

4] Finally, one other win to the #79:

Since your main goal is to use these for sliding dovetails, the 79 has
a nice little depth stop that is pretty durn easy to bend to correct angle
as a guide for the working the side of the dovetail slot.

Or, even better, keep the original, and make yourself an set
of guides in an assortment of angles our of sheet metal.

Needless to say, this is all just my opinion on these things, but I hope
there's something helpful here.
Nichael 
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