LS fifth gear opinions

[Fox351]

I have a b16 hydro transmission and I am rebuilding it. I have been looking around and found that some people put an LS fifth gear in it. I was wondering what the opinions of IA were about this modification. I can see the benifit of having that gear when cruising and on the highway for MPG. I was wondering on the performance side what would be the downfall? I can't see a street car reaching 5th gear on the drag strip or in a roll race( only place I plan on racing ) but can see it reaching it on an open straight on an autcross track. I was wondering what you guys think.

[SPOOLIN]

if will be better than an ls 5th in an ls tranny because you will have the higher final drive but it will still be a big difference, its mainly for gas mileage.

[Starrfire]

I've done it to the past few I've had. Only way to roll any more. About $300 for parts and labor to put one it. You'll need the gear on the main and countershaft, and then it's not a huge amount of labor to get the gear off and the other on so go for it.