you batter overhaul the engine with taiwan piston , chinese piston comes with a name "Righway", first search taiwan piston (i forget there name) and if you dont found taiwan then go for chinese , but dont go for a local made piston name "strong" and if you can afford then go for a japanese piston name "ART" , i suggest you go for a taiwan piston
use NPR japan rings , never compromise on rings , engine comes with "TP" rings from factory , but i suggest you go for NPG rings , they are far batter then "TP"
use supreme valve (local made) they are good , but dont change the valve seals and valve guides,
if your engine is noisy , if it has a loud sound on high RPM then you must change the crank shaft bearing , and also head came shaft bearings , use chinese crank shaft bearings and thrust bearings , i dont know alto comes with connecting rod bush or comes with presses piston ring , if it comes with rod bush then change them also , head cam shaft does not comese with portable bearings , you need to take it to the machine shop and he will guide you ho to make bush for it ,
if your engine mixes water with oil or vice versa then you must reface the head as well , but if wont then dont do it , i know machine shops will force you to do it , but i suggest dont do it uncessarly
also change the oil pump assambly , dont change the complete pump , just change its inner gears ,
use original gas kit and local made jan kit , and also use original engine seals , use original valve seals , corteco or NOK are original brands in seals , dont compromise on valve seals ,
change timing belt if necessary ,
check for water pump , if found sone sign of leaks then change it with GMB water pump
i gave you these suggestion as per my experence , i personally rebuilt my car cultus engine in under 10000 RS , i go to mechanic and he says it will cost more than 35000 ,
dont change the engine with kabli , its a kind of gamble , which rarelly pay back , and i know pathans , they repair the engine and sale them saying its in out class condition , but if you still want to replace then go to "mithu khan kaa ahata" in sadar rwp to buy a new one , but i wont recomend that
https://www.pakwheels.com/forums/performance-modification-tune-up-preventive-maintenance/181721-cultus-engine-body-overhaul-rebuild
check my form , i am also rebuilding my cultus
thanks