Need opinions on build (which motor)

[Varinn]

I've spent countless hours researching this subject trying to figure out what route to go with my car but I cannot make up my mind, so I'm looking for input. 1984 325e, bone stock except for a MarkD chip and 3.25LSD. I have in my garage the entire motronic 1.3 conversion setup, so all electronics, cooling system, fuel system etc are from a 1987 325i. I also have a set of longtube headers that will be used in the build, exhaust from there back is yet to be determined.

I have 3 realistic options, and my mind is currently battling between #1 and #3, as the 731 head just needs so much work over the others. From a purely performance/cost/tuning standpoint, I need input.

Option #1:
eta block
323i head (e21, 200casting, stock 323i cam)
323i intake, TB, etc
m1.3 electronics
longtube headers into custom exhaust

The good: Known head from a friend's e21 (BMW tech). Head can be had for $150 + gasket set and timing belt kit (and any potential work it may need). Good CR and decent torque around town. Head would include the 323i intake, but 325i electronics.

The bad: 200 cast head, lowest flow rate due to early port and valve sizing meaning shit top end breathing compared to the m20b25

Option #2:
eta block
323i head (e30, 731 casting, 288 Shrick cam)
325i intake, TB, etc
m1.3 electronics
longtube headers into custom exhaust

The good: Good flow rates, aggressive cam for good top end power

The bad: Expensive! $375 for the head and it is known to burn oil. Add in the gasket set, timing belt, machinework, valve guides/seals, rockers, and port work to match 325i this quickly becomes and expensive job

Option #3:
bone stock 87 m20b25/intake
m1.3 electronics
longtube headers into custom exhaust

The good: Known good motor from a friend (BMW tech), well maintained coming out of a recently rear ended car. $150 for the motor. No fuckin' around, guaranteed performance with little hassle. However, I would likely deck the head and install an adjustable cam wheel to gain a little comp ratio.

The bad: piss poor match to my 3.25LSD, so a diff would be in order

[MR 325]

I would definitely rule out the first option. Option number 3 makes the most sense if you're on a budget, option number 2 would be the most fun! With option 2 or 3 you're going to want to swap in a 3.73 diff.

[digger]

how about eta bottom and b25 pistons with 885 head. deck the block ~2mm.

[Varinn]

how about eta bottom and b25 pistons with 885 head. deck the block ~2mm.

that's a very tempting idea for building a high comp motor, my issue with it is downtime. I've never worked on a bottom end before and don't know the costs or skills involved with the machining and new bearings. What's the final displacement and CR with that?

At the moment #3 makes the most sense as I can fully prep the motor beforehand in my garage and drop it in effectively overnight with no tuning issues.