I'm kinda new in this field but here are my 2cents:
Since you're already going to swap engine, might as well go for Levin or Trueno engine lah. Provided if you've got the budget... If budget too tight, then look for ori SEG engine loh, provided its in good cond.
Here's how the engines/h-cuts rank in price for NA:
4AGE 16V (non-TVIS) RM1.5K-RM2K
4AGE 20V Silvertop RM2.5K - RM3K
4AGE 20V Blacktop RM3K - RM4K
Also, remember that you need another RM1K for workmanship, wear&tear parts and other expenses, no matter what engine/h-cut. If the engine/h-cut is in bad cond and needs minor overhaul, be prepared for another RM500-700 for that.
So if you have RM3K max, the 4AGE 16V non-TVIS is the way to go. If you have RM3.5K to RM4K, then 20V SVT or 20V BT, provided if you can find a cheap and good condition h/cut. A few guys have been telling me that 16V is better and lasts longer than 20V BT. Some guys even have proper tuned 16V that can rundown a 20V BT anytime. Some said 20V SVT is more stronger than 20V BT, which is why some tuners choose 20V SVT for heavy modding.
Remember, I'm not a pro here but those are my 2cents. Btw, the prices are based from Ipoh chopshop pricings. You may be able to get cheaper h/cuts from KL, but gotta transport it back to Ipoh leh... ~Cheers!
