M16a headgasket

Hi guys, 
despite hoping it wasn't, I'm airing towards thinking my head gasket has gone. It's yet to over heat on the guage so now is the time to act!
My symptoms are;

Water sloshing noise from inside the cabin when revved,
Smelling very (very) hot after every drive especially higher speed motorway journeys, 
Coolant expanding into the expansion tank when hot but not being sucked back in when the engine cools even when left overnight!

What I've done so far;
M16a Liana conversion back at Christmas with a brand new radiator fitted at that time.
New genuine rad cap and thermostat last week.
Waterpump removed, inspected and refitted (perfect condition).
Coolant system cleaned and flushed through using a Holts additive.

I have diagnosed my viscous coupling is not working, while I will get a new one, as a temporary measure I purposely seized it up so the fan is working permanently. I wouldn't recommend this normally as it feels like it's sucked 10bhp from the engine and makes loads of noise but for a diagnosis purpose, it's not changed my symptoms at all.

I have also read about the pipe in the expansion bottle getting longer over time and touching the bottom of the bottle, blocking the coolant returning into the rad. While mine had definitely got longer, I cut an inch off to be safe but this also has not changed my symptoms at all. 

So we are where we are... I'm almost convinced now that it is the head gasket.

I guess my main question is having done the m16a conversion, I'm assuming the gasket is different to the m13a? I no longer have the reg of the donor car for parts... or is it as easy as asking for a gasket for an engine rather than a car? 
A secondary question is regarding the work... I'm pretty confident but never done a head gasket on a chain engine,  do you have to change the tensioner? Assuming it's hydraulic? What about the chain sliders?

Any thoughts or tips would be greatfully received!

Many thanks
Ben

I can't see why it would be a different gasket. The increase in capacity is from a longer stroke rather than a bigger bore. The cylinder heads are all identical. But if in doubt, scour the calssifieds for a similar age liana for sale and use that reg to order.

I'm not seeing/hearing any evidence of a leaking head gasket ...

- do you have signs of oil/coolant cross contamination?
- have you tested the coolant for the presence of hydrocarbons?
- have you done a compression test and leak down tests?

Coolant sloshing sounds in the cabin when revved is a sign of low coolant in the heater circuit.

Coolant not returning from the expansion tank will cause low coolant, which can cause the sloshing sounds, any cooling system leak can cause coolant not to return from the expansion bottle and the most common cause of coolant not returning is a defective radiator cap.

Eliminate the simple things, do the necessary tests before you pull the head.

If as reported you have either inspected or replaced all the ancillary cooling system parts then yes it's time for a head gasket for. Busta is onto a winner with the suggestion of a borrowed reg for parts orders.

As Fordem says, rad cap! They are a common failure with the same symptoms.

Guys read the original post. It has brand new rad cap I know it's a common issue.
New genuine rad cap
New genuine thermostat
Water pump is in perfect condition
The radiator was new at Christmas.
Engine was out of a 70k mile car.

The rad level is low everytime when checked and its always exactly the amount that is in the expansion bottle but hasn't returned...

I've not done a leak down test nor do I have the equipment.
I'm not particularly worried about doing the head gasket, I've done lots in the past (old fords), I was more after tips on the job itself and acquiring the parts.

Thanks for your reply

Ben