You need to investigate further,for example the TYRE size which were on the Fourtrack is irrelevant, what you need to know is the WHEEL measurements-ie;

6jx15, 6.5jx15, 7jx15.....this is the RIM widthx diameter, this is the critical size and will determine the tyre size variables.

You will also need to know the centre bore as this is critical.
for example the WHEELS on my Terios mk3 are ;
5.114.3.7jx16.66.6
This means; 5 stud.114.3PCD.7"wide x16"dia with 66.6mm centre bore.

Do you know the current size wheels you have?? If you have thoise details, PM me and I will find out for you what the variables are

SOME READING FOR YOU
Bolt circle (pcd)

4 Hole Pattern

5 Hole Pattern
The bolt circle is the circle determined by the positions of the bolts; the center of every bolt lies on the circumference of the bolt circle.
The important measurement is the "pitch circle diameter" (PCD), usually expressed in millimeters, although inches are sometimes used. For a 4- or 6-bolt car, this measurement is merely the distance between the center of two diametrically opposite bolts. In the 4-bolt picture to the right, this would be the distance between holes #1 and #4. Some basic geometry is needed to find the center of a 5-bolt pattern: But basically, the PCD can be found by multiplying the center distance between any two adjacent holes by 1.701.
Generally, the PCD can be calculated for any wheel from the number of bolts (n) and the measured center distance between two adjacent bolts (d) as; PCD = d / SIN(180/n).
A 1974 MG B is a 4/4.5" (4/114.3) car, meaning it is, again, a 4-bolt pattern with a 4.5" or 114.3 mm bolt circle.
The most common PCD values are 100 mm and 114.3 mm. This difference arises from the manufacturers' measurement convention - whether they are designing around metric values (100 mm) or imperial values (4.5 inches, i.e. 114.3 mm). Note: there are exceptions and some metric car models have imperial rims (4.5").
[edit] Lug nuts or bolts
Another thing considered when new wheels are purchased is proper lug nuts or bolts. They are usually either flat, tapered (generally at 60 degrees and referred to as conical seat), or ball seats, meaning the mounting surfaces are flat, tapered, or spherical respectively. For example, most Mercedes have ball lug seats from the factory while most aftermarket wheels have a tapered lug design. If you buy aftermarket wheels for a Mercedes make sure you get the proper lug nuts for the wheel or the wheel will not be properly centered. Some manufacturers (e.g. Toyota and Lexus) have used taper lug nuts for steel wheels and flat seated lug nuts for alloy wheels.
Some aftermarket wheels will only fit smaller lug nuts, or not allow an ordinary lug nut to be properly torqued down because a socket will not fit into the lug hole. Tuner lug nuts were created to solve the problem. Tuner lug nuts utilize a special key to allow removal and installation with standard lug wrench or socket. The design of tuner lug nuts can range from bit style to multisided or spline drive, and are sometimes lightweight for performance purposes. A variation is the "locking wheel nut", which is almost universally used for alloy wheels in the United Kingdom. One standard lug nut on each wheel is replaced with a nut which requires a special and unique key (typically a computer-designed, rounded star shape) to fit and remove the nut. This helps to discourage theft of wheels. However, universal removal tools are available which grip the head of the locking nut using a hardened left-hand thread. The success of these depends on whether there is room to use it in the lug hole, and whether the manufacturer has incorporated a free-spinning outer casing to the lock. Keeping an appropriate tool to lock and unlock aftermarket nuts, and a spare set of nuts, with the spare tire in the boot of the car is recommended by manufacturers.
[edit] Offset
The offset, measured in millimeters, can be negative or positive, and is the distance from the hub-mounting surface to the rim's true centerline. A positive offset means the hub-mounting surface is closer to the outside edge of the wheel, i.e. the wheel wraps around the hub and brake hardware more deeply; a negative offset means the hub-mounting surface is closer to the inside edge of the wheel and wheel sticks outwards more than inwards. When selecting aftermarket wheels, a wheel with too little positive offset will be closer to the fender, and one with too much positive offset will be closer to the suspension components. Wheel width, offset and tire size all determine the way a particular wheel/tire combination will work on a given car. Offset also affects the scrub radius of the steering and it is advisable to stay within the limits allowed by the vehicle manufacturer. Because wheel offset changes the lever-arm length between the center of the tire and the centerline of the steering knuckle, the way bumps, road imperfections and acceleration and braking forces are translated to steering torques (bump-steer, torque-steer, etc) will change depending on wheel offset. Likewise, the wheel bearings will see increased thrust loads if the wheel centerline is moved away from the bearing centerline.