Originally Posted by InfiniteDice
Sorry as for types of engines that would be a direct swap? Off the top of my head i'd say the the 320i 325e 325i 325ix, 318 would fit obviously not sure about the tranny.
IXs have an iX specific block and oil pan, meaning you can't just drop in any m20 and damn sure you can't use an m10/42(318) without doing some major custom work.
with an iX you rule out any possible cost effective motor swaps, you'd have to spend a fortune in custom work, anything is possible with enough money.
Your best options are building an m20 or going turbo.