IMO the Finnish tank conversion is a very ingenuous use of old T-54/T-55 chasis. The Israelis are also masters at this. They have a lot of old US made M113 APC's and captured T-54/T-55 tanks, and found that the M113's could be destroyed by a RPG round. So they converted the T-54/T-55's to APC's:
And the M113 APC's to air defense units:
The M113 was originally armed with just a machinegun. They replaced it with a 20mm Volcan gun, EL/M 2106 radar, and 4xSAM launcher box.
The General Dynamics 20mm Vulcan gun can fire at rate of 3,000 rounds/min. Armed with APDS rounds, it has an effective range of up to 3.5km.
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So the original question was Pakistani's ground force's anti-air capability. According to Pakistani defense web site, Pakistani has over 850 M-113P with local manufacturing facility:
Plus pending order for up to 2,000 "Talha" APC's by 2010:
IMO there's no reason why they cannot copy Israeli concept and convert some APC's to short-range anti-air units. They can purchase technology from the PRC, such as those used on the TY-90:
Just add some AA guns to it and you're good to go.
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Here's one more T-55 tank conversion (recycled chasis?) from Poland:
The S-125/Newa SC replaces old SA-3 system with updated digital electronics, and mount the missile launcher on a T-55 chasis.
Yugoslavia was known to operate 14 SA-3 batteires with ~60 launchers, credited with a F-117 downing.