Hello there, 
I decided to make my own GTA San Andreas beta weapon pack. Just download and replace.
It isn't the final version. More updates to come! Almost forgot, you decide by yourself which weapon do you want to use. Picture of all models in this pack can be found in the picture section on this site.
The pack contains:
Based on game files
Bat with nails
Different Sawn off
PSG1 sniper rifle
Based on cutscenes
Wooden bat
Camera
Glock
Better textured Golf Club
M4
Parachute
Shovel
Based on weapon icon
AK47 without the stock
I have a doubt if it was in the beta, but you can skip this model

PSG1 sniper rifle (again)
Basically, icon by itself represents more PSG1 rather than in-game sniper rifle. Unused model was found in the game files

Based on screenshots
Uzi from Vice City
Spray can
By default this texture file is unused, so it has an original one

Additional information
All these models were found in the game files. Converted, fixed and polished by me. Every weapon has new and shiny icon. Camera and sniper PSG1 have HQ scope textures.

Weapons like bat with nails, Sawn off, PSG1, M4 (and MP5-K, which is not ready yet) were taken from the Manhunt game by the devs. For some reasons, these models, in GTA game files, use some kind of dirt texture. That is why I took original textures from the Manhunt game. BTW they fit perfectly without any modifications, since the models are the same.

Credits
This pack was made by Vadim M.

GTA San Andreas Beta weapons analysis