Morning misfire and what tye of bolt is that?

Hello all Land Rovers and Rangie fans. had my thor 2000 w reg 4.0 v8 rangie now for 5 years and no major problems but now have a misfire in the morning for about 40 secs and then runs fine.
recently that pain in the arse heating system under the throttle body started to leak (all ready changed this once) and as it was so cold I put off sorting it out until it was warmer(this was Dec 10th). Went on a run and overheated. Filled it back up and ran ok. Since then its started to miss in the morning and slight coolant loss.
I think its a head gasket. Also got gas so its a pain getting plugs in and out to diagnose cylinders. Also have oil leaks from the rocker covers so have come to the conclusion I need a full top end rebuild. this is no problem for me as I've rebuilt a few engines and done several heads, but want to know what are the bolts that keep the exhaust manifolds on and do you need to take the manifold to exhaust connection appart to get the heads off when working above. Also seen several top end kits on Ebay but land rover dont do a complete kit. Are these any good. Thanks for any help.

head gasket yes but also possible block me personaly remove the heater under the plenum and throw it in the bin only really needed for artic countrys!
cam kits stick with genuine parts best you can get and piper cams